[Android Q&A, Help & Troubleshooting] s0f0s:
Hello! I am trying to build LineageOS 15 from sources for Sony Xperia Z3Dual. I have several years of c/c++ programming experience but this is my first Android project. So despite reading several howtos it is possible that I made some stupid and/or funny mistakes :)

I cloned the LOS 15

repo init -u git://github.com/LineageOS/android.git -b lineage-15.0

and added several Sony Xperia Z3 repositories with localmanifest:

<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<!--Devices-->
<project path="device/sony/z3"
name="x-keita/android_device_sony_z3" remote="github"
revision="lineage-15.0_r1" />
<!--Devices commons-->
<project path="device/sony/shinano-common"
name="x-keita/android_device_sony_shinano-common" remote="github"
revision="lineage-15.0_r1" />
<project path="device/sony/msm8974-common"
name="x-keita/android_device_sony_msm8974-common" remote="github"
revision="lineage-15.0_r1" />
<!--Kernels-->
<project path="kernel/sony/msm8974"
name="x-keita/android_kernel_sony_msm8974" remote="github"
revision="lineage-15.0" />
<!--Vendors-->
<project path="vendor/sony"
name="x-keita/proprietary_vendor_sony" remote="github"
revision="lineage-15.0" />
<!--Hardware-->
<project path="hardware/sony/thermanager"
name="LineageOS/android_hardware_sony_thermanager" remote="github"
revision="lineage-15.0" />
</manifest>

then

$ . build/envsetup.sh
including device/generic/car/car-arm64/vendorsetup.sh
including device/generic/car/car-armv7-a-neon/vendorsetup.sh
including device/generic/car/car-x86_64/vendorsetup.sh
including device/generic/car/car-x86/vendorsetup.sh
including device/generic/mini-emulator-arm64/vendorsetup.sh
including device/generic/mini-emulator-armv7-a-neon/vendorsetup.sh
including device/generic/mini-emulator-x86_64/vendorsetup.sh
including device/generic/mini-emulator-x86/vendorsetup.sh
including device/sony/z3/vendorsetup.sh
including vendor/lineage/vendorsetup.sh
including sdk/bash_completion/adb.bash

But Lunch menu has only one item

$ breakfast
including vendor/lineage/vendorsetup.sh

You're building on Linux

Lunch menu... pick a combo:
1. full-eng

Which would you like? [aosp_arm-eng] ^C

Direct call results in error:

$ brunch z3
including vendor/lineage/vendorsetup.sh
Trying dependencies-only mode on a non-existing device tree?

============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=8.0.0
LINEAGE_VERSION=15.0-20180116_000047-UNOFFICIAL-z3
TARGET_PRODUCT=lineage_z3
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_PLATFORM_VERSION=OPR1
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a-neon
TARGET_CPU_VARIANT=krait
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_2ND_ARCH=x86
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.13.0-21-generic-x86_64-with-Ubuntu-17.10-artful
HOST_CROSS_OS=windows
HOST_CROSS_ARCH=x86
HOST_CROSS_2ND_ARCH=x86_64
HOST_BUILD_TYPE=release
BUILD_ID=OPR3.170623.013
OUT_DIR=/home/user/Android/roms/los15/out
AUX_OS_VARIANT_LIST=
============================================
make: Entering directory '/home/user/Android/roms/los15'
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=8.0.0
TARGET_PRODUCT=lineage_z3
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a-neon
TARGET_CPU_VARIANT=krait
HOST_ARCH=x86_64
HOST_2ND_ARCH=x86
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.13.0-21-generic-x86_64-with-Ubuntu-17.10-artful
HOST_CROSS_OS=windows
HOST_CROSS_ARCH=x86
HOST_CROSS_2ND_ARCH=x86_64
HOST_BUILD_TYPE=release
BUILD_ID=OPR3.170623.013
OUT_DIR=/home/user/Android/roms/los15/out
============================================
ninja: no work to do.
ninja: no work to do.
Environment variable BUILD_NUMBER was modified (a59a0e5c70 => 39348e7c4f), regenerating...
[9/1020] including ./cts/Android.mk ...
cts/apps/CtsVerifier/Android.mk:72: warning: FindEmulator: find: `cts/apps/CtsVerifier/src/com/android/cts/verifier/backup': No such file or directory
build/core/java_common.mk:88: warning: FindEmulator: cd: cts/hostsidetests/appsecurity/test-apps/WriteExternalStorageApp/cts/hostsidetests/appsecurity/test-apps/WriteExternalStorageApp/res: No such file or directory
build/core/java_common.mk:88: warning: FindEmulator: cd: cts/hostsidetests/backup/assets: No such file or directory
cts/hostsidetests/os/test-apps/StaticSharedNativeLibProvider/Android.mk:23: warning: FindEmulator: find: `cts/hostsidetests/os/test-apps/StaticSharedNativeLibProvider/src': No such file or directory
cts/hostsidetests/os/test-apps/StaticSharedNativeLibProvider1/Android.mk:23: warning: FindEmulator: find: `cts/hostsidetests/os/test-apps/StaticSharedNativeLibProvider1/src': No such file or directory
cts/tests/tests/contactsproviderwipe/Android.mk:33: warning: FindEmulator: find: `cts/tests/tests/contactsproviderwipe/common/src': No such file or directory
cts/tests/tests/telecom3/Android.mk:37: warning: FindEmulator: find: `cts/tests/tests/telecom/src/android/telecom/cts/MockDialerActivity.java': No such file or directory
[338/1020] including ./external/toybox/Android.mk ...
awk: line 1: syntax error at or near ,
[370/1020] including ./frameworks/av/media/libaaudio/Android.mk ...
frameworks/av/media/libaaudio/examples/input_monitor/static/Android.mk: warning: input_monitor: unusual tags examples
frameworks/av/media/libaaudio/examples/write_sine/static/Android.mk: warning: write_sine: unusual tags examples
[404/1020] including ./frameworks/base/Android.mk ...
./frameworks/base/Android.mk:866: warning: FindEmulator: find: `frameworks/opt/telephony/src/java/android/provider': No such file or directory
./frameworks/base/Android.mk:875: warning: FindEmulator: find: `frameworks/opt/telephony/src/java/android/provider': No such file or directory
./frameworks/base/Android.mk:880: warning: FindEmulator: find: `frameworks/opt/telephony/src/java/android/provider': No such file or directory
./frameworks/base/Android.mk:885: warning: FindEmulator: find: `frameworks/opt/telephony/src/java/android/provider': No such file or directory
[583/1020] including ./lineage-sdk/Android.mk ...
./lineage-sdk/Android.mk:152: warning: FindEmulator: find: `lineage-sdk/dummy': No such file or directory
build/core/droiddoc.mk:132: warning: FindEmulator: find: `build/tools/droiddoc/templates-sdk': No such file or directory
[754/1020] including ./system/sepolicy/Android.mk ...
./system/sepolicy/Android.mk:95: warning: BOARD_SEPOLICY_VERS not specified, assuming current platform version
[1020/1020] including ./vendor/sony/z3dual/Android.mk ...
build/core/Makefile:54: warning: Duplicate header copy: /home/user/Android/roms/los15/out/target/product/z3/obj/include/cld80211-lib/cld80211_lib.h
build/core/Makefile:54: warning: Defined in: hardware/qcom/wlan-caf/cld80211-lib/Android.mk hardware/qcom/wlan-caf/cld80211-lib/Android.mk
No private recovery resources for TARGET_DEVICE z3
platform_testing/build/tasks/tests/instrumentation_metric_test_list.mk: warning: continuous_instrumentation_metric_tests: Unknown installed file for module perf-setup.sh
platform_testing/build/tasks/tests/instrumentation_test_list.mk: warning: continuous_instrumentation_tests: Unknown installed file for module RecyclerViewTests
platform_testing/build/tasks/tests/instrumentation_test_list.mk: warning: continuous_instrumentation_tests: Unknown installed file for module SettingsFunctionalTests
platform_testing/build/tasks/tests/instrumentation_test_list.mk: warning: continuous_instrumentation_tests: Unknown installed file for module LauncherFunctionalTests
platform_testing/build/tasks/tests/native_metric_test_list.mk: warning: continuous_native_metric_tests: Unknown installed file for module perf-setup.sh
test/vts/tools/build/tasks/vts_package.mk:216: warning: FindEmulator: cd: vendor/google_vts/testcases: No such file or directory
test/vts/tools/build/tasks/vts_package.mk:216: warning: FindEmulator: cd: vendor/google_vts/testcases: No such file or directory
test/vts/tools/build/tasks/vts_package.mk:216: warning: FindEmulator: cd: vendor/google_vts/testcases: No such file or directory
./test/vts/utils/python/archive/Android.mk:28: warning: overriding commands for target `default'
./test/vts/runners/host/tcp_server/Android.mk:19: warning: ignoring old commands for target `default'
./test/vts/utils/python/coverage/Android.mk:28: warning: overriding commands for target `default'
./test/vts/utils/python/archive/Android.mk:28: warning: ignoring old commands for target `default'
ninja: error: '/home/user/Android/roms/los15/out/target/product/z3/utilities/init_sony', needed by '/home/user/Android/roms/los15/out/target/product/z3/boot.img', missing and no known rule to make it
03:03:10 ninja failed with: exit status 1
build/core/main.mk:21: recipe for target 'run_soong_ui' failed
make: *** [run_soong_ui] Error 1
make: Leaving directory '/home/user/Android/roms/los15'

#### make failed to build some targets (02:23 (mm:ss)) ####

What could be possible reason for this? What I did in a wrong way?