RepoPick : Add support for git pull

Allow user to git pull patchsets and dependencies.

Change-Id: If5520b45fe79836eac628b3caf0526f11f8953d9
(cherry picked from commit df646304bdcef329e3fe7c12b68107de1f4cd42a)
Allow devices to specify certain ro. props via TARGET_INIT_VENDOR_LIB

This modifies buildinfo.sh to not set model, name, description, and
fingerprint in build.prop. These can then be set via custom init
lib.
This also fixes ota_from_target_files to function without these
props being preset.

Change-Id: I945b2c38e60b207d2d0f82b34f4f230ac21b0657
add option to use -pipe

Same as this patch http://review.pac-rom.com/#/c/1008/

Usage:
export TARGET_USE_PIPE=true && ./build-pac.sh

Change-Id: Id5b3ade07364cb5be33172fc7f99f2a6c80b0e63
build: no longer build emulator by default

This is just increasing build times when most people are not using it.
Let's speed up builds a bit.

Building emulator should still be possible by appending BUILD_EMULATOR=true
to the build command

Change-Id: Ibd8e2b90455bd603a691c7b95466068b6fae212a
Allow defining multiple GCC O Levels [1/2]

Available GCC Optimization Levels
    -Os
    -O2 (Default)
    -O3

PS2: Derp fix
PS3: Derp fix 2.0

Change-Id: I55fa04026df24841b9d67325242ce3cb460726a1
Signed-off-by: Lokesh Chamane <lokesh.c703@gmail.com>