Issue 1:
ninja: Entering directory `out/R'
[22/282] CC obj/vendor/crashpad/util/obj/vendor/crashpad/util/crashpad_util.gen/util/mach/crashpad_util.child_portUser.o
FAILED: ../../vendor/llvm-build/Release+Asserts/bin/clang -MMD -MF obj/vendor/crashpad/util/obj/vendor/crashpad/util/crashpad_util.gen/util/mach/crashpad_util.child_portUser.o.d -DENABLE_WEBRTC -DNDEBUG -DV8_USE_EXTERNAL_STARTUP_DATA -DSK_SUPPORT_LEGACY_GETTOPDEVICE -DSK_SUPPORT_LEGACY_BITMAP_CONFIG -DSK_SUPPORT_LEGACY_DEVICE_VIRTUAL_ISOPAQUE -DSK_SUPPORT_LEGACY_N32_NAME -DSK_SUPPORT_LEGACY_SETCONFIG -DSK_IGNORE_ETC1_SUPPORT -DSK_IGNORE_GPU_DITHER -DUSE_OPENSSL -I../../vendor/crashpad -Iobj/vendor/crashpad/util/crashpad_util.gen -I/Users/kendall/code/third-party/electron/vendor/brightray/vendor/download/libchromiumcontent/src -I../../vendor/crashpad/compat/mac -I../../vendor/crashpad/compat/non_win -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -fasm-blocks -mpascal-strings -O2 -gdwarf-2 -Werror -mmacosx-version-min=10.9 -arch x86_64 -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wno-deprecated-declarations -Wno-unneeded-internal-declaration -std=c99 -fcolor-diagnostics -fno-inline -fno-omit-frame-pointer -fno-builtin -fno-optimize-sibling-calls -c obj/vendor/crashpad/util/crashpad_util.gen/util/mach/child_portUser.c -o obj/vendor/crashpad/util/obj/vendor/crashpad/util/crashpad_util.gen/util/mach/crashpad_util.child_portUser.o
In file included from obj/vendor/crashpad/util/crashpad_util.gen/util/mach/child_portUser.c:9:
In file included from obj/vendor/crashpad/util/crashpad_util.gen/util/mach/child_port.h:65:
In file included from ../../vendor/crashpad/util/mach/child_port_types.h:18:
../../vendor/crashpad/compat/mac/mach/mach.h:56:2: error: Update this file for new exception types
#error Update this file for new exception types
^
1 error generated.
[22/282] CC obj/vendor/crashpad/util/obj/vendor/crashpad/util/crashpad_util.gen/util/mach/crashpad_util.child_portServer.o
FAILED: ../../vendor/llvm-build/Release+Asserts/bin/clang -MMD -MF obj/vendor/crashpad/util/obj/vendor/crashpad/util/crashpad_util.gen/util/mach/crashpad_util.child_portServer.o.d -DENABLE_WEBRTC -DNDEBUG -DV8_USE_EXTERNAL_STARTUP_DATA -DSK_SUPPORT_LEGACY_GETTOPDEVICE -DSK_SUPPORT_LEGACY_BITMAP_CONFIG -DSK_SUPPORT_LEGACY_DEVICE_VIRTUAL_ISOPAQUE -DSK_SUPPORT_LEGACY_N32_NAME -DSK_SUPPORT_LEGACY_SETCONFIG -DSK_IGNORE_ETC1_SUPPORT -DSK_IGNORE_GPU_DITHER -DUSE_OPENSSL -I../../vendor/crashpad -Iobj/vendor/crashpad/util/crashpad_util.gen -I/Users/kendall/code/third-party/electron/vendor/brightray/vendor/download/libchromiumcontent/src -I../../vendor/crashpad/compat/mac -I../../vendor/crashpad/compat/non_win -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -fasm-blocks -mpascal-strings -O2 -gdwarf-2 -Werror -mmacosx-version-min=10.9 -arch x86_64 -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wno-deprecated-declarations -Wno-unneeded-internal-declaration -std=c99 -fcolor-diagnostics -fno-inline -fno-omit-frame-pointer -fno-builtin -fno-optimize-sibling-calls -c obj/vendor/crashpad/util/crashpad_util.gen/util/mach/child_portServer.c -o obj/vendor/crashpad/util/obj/vendor/crashpad/util/crashpad_util.gen/util/mach/crashpad_util.child_portServer.o
In file included from obj/vendor/crashpad/util/crashpad_util.gen/util/mach/child_portServer.c:12:
In file included from obj/vendor/crashpad/util/crashpad_util.gen/util/mach/child_portServer.h:65:
In file included from ../../vendor/crashpad/util/mach/child_port_types.h:18:
../../vendor/crashpad/compat/mac/mach/mach.h:56:2: error: Update this file for new exception types
#error Update this file for new exception types
^
1 error generated.
[22/282] CXX obj/vendor/node/src/node.node_javascript.o
ninja: build stopped: subcommand failed.

Python: 2.7.10

Node: v0.12.7

Xcode: 7A218

This seems to have to do with Xcode 7. The last time it was working, I was building with Xcode 6.

Issue 2:
ninja: Entering directory `out/D'
[23/505] OBJCXX obj/vendor/breakpad/src/common/mac/dump_syms.dump_syms.o
FAILED: ../../vendor/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/vendor/breakpad/src/common/mac/dump_syms.dump_syms.o.d -DHAVE_MACH_O_NLIST_H -DNDEBUG -DV8_USE_EXTERNAL_STARTUP_DATA -DSK_SUPPORT_LEGACY_GETTOPDEVICE -DSK_SUPPORT_LEGACY_BITMAP_CONFIG -DSK_SUPPORT_LEGACY_DEVICE_VIRTUAL_ISOPAQUE -DSK_SUPPORT_LEGACY_N32_NAME -DSK_SUPPORT_LEGACY_SETCONFIG -DSK_IGNORE_ETC1_SUPPORT -DSK_IGNORE_GPU_DITHER -DUSE_OPENSSL -DDEBUG -DCOMPONENT_BUILD -DGURL_DLL -DSKIA_DLL -DUSING_V8_SHARED -DWEBKIT_DLL -I../../vendor/breakpad/src -I../../vendor/breakpad/src/common/mac -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -funsigned-char -fasm-blocks -mpascal-strings -O0 -gdwarf-2 -Werror -mmacosx-version-min=10.8 -arch x86_64 -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wno-deprecated-declarations -Wno-deprecated-register -Wno-unused-private-field -Wno-unused-function -std=c++11 -stdlib=libc++ -fno-exceptions -fcolor-diagnostics -c ../../vendor/breakpad/src/common/mac/dump_syms.mm -o obj/vendor/breakpad/src/common/mac/dump_syms.dump_syms.o
In file included from ../../vendor/breakpad/src/common/mac/dump_syms.mm:36:
In file included from ../../vendor/breakpad/src/common/mac/dump_syms.h:38:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h:10:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSArray.h:5:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:19:21: error: expected a type
- (id)copyWithZone:(nullable NSZone *)zone;
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:25:28: error: expected a type
- (id)mutableCopyWithZone:(nullable NSZone *)zone;
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:32:4: error: expected a type
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder; // NS_DESIGNATED_INITIALIZER
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:53:4: error: expected a type
- (nullable id)replacementObjectForCoder:(NSCoder *)aCoder;
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:54:4: error: expected a type
- (nullable id)awakeAfterUsingCoder:(NSCoder *)aDecoder NS_REPLACES_RECEIVER;

Python: 2.7.10

Node: v0.12.7

Xcode: 7A121l

Builds successfully if you replace Xcode.app with Xcode 6 and repeat the bootstrapping and build process.