GitLab

This is the first step to build 32-bit libraries in a 64-bit product.
It will work like this:
1) In the product's BoardConfig.mk, define:
TARGET_2ND_ARCH, TARGET_2ND_ARCH_VARIANT, TARGET_2ND_CPU_VARIANT.
The build system uses those variables to set up an additional compiler
environment for the second arch.

2) When parsing Android.mks, the build system sets up rules to build a
module for both the 1st arch and the 2nd arch, unless it's explicitly
asked to skip so.
Android.mk will be adapted if there is additional rule of generating
source files.
The build system will accept arch-specific LOCAL_ variables, such as
LOCAL_CFLAGS_arm, LOCAL_CFLAGS_armv7-a-neon, LOCAL_CFLAGS_cortex-a15,
LOCAL_CFLAGS_aarch64 etc. Modules use such variables to set up build for
various archs at the same time.

3) Install binary of the 2nd arch by adding "<module_name>:32" to
PRODUCT_PACKAGES. All 2nd-arch libraries linked in by "<module_name>:32"
will be installed automatically.

Bug: 11654773
Change-Id: I2df63cd5463a07bf5358bee2a109f8fb9590fe30

Conflicts:
	core/combo/TARGET_linux-arm.mk