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

PS2: Let's keep the darwin warning.

Change-Id: Ibd8e2b90455bd603a691c7b95466068b6fae212a
Signed-off-by: Andrew Warfield <hiasant@gmail.com>
build: Set ccache base to build top

This enables ccache sharing between different build tree paths.

Change-Id: I99636bdd2779a6ccf0649f027e35cf67df44b6ae
build: Optimize for Krait

PS1:Add standard method for enabling mfpu and mcpu code optimization

Conflicts:
	core/combo/arch/arm/armv7-a-neon.mk
	core/combo/arch/arm/armv7-a.mk

PS2:build: Enable Bionic optimizations on Cortex platforms

 * Enable the new NEON optimizations in Bionic when
   TARGET_ARCH_VARIANT_CPU is set.
 * NEON memcpy() optimization is disabled on A15 due to a regression.

Change-Id: I4862695812a70b75bdabc4398cb592157f3913c6

PS3:build: move bionic optimizations to NEON makefile

Change-Id: Idd495ddbb49f67fef5496456803263f8a23643c5

PS4:build: Relax Cortex CFLAGS

 * Always set march=armv7-a
 * Use mtune instead of mcpu. Bad code is generated on A15 otherwise.

Change-Id: Idf8ced8eb0e9d3d4676ca8ec69bf56aed5533bf4

PS5:build: Cleanup CPU-specific optimizations

 * TARGET_ARCH_CPU_VARIANT was a Linaro thing. Now that Android
   introducted TARGET_CPU_VARIANT, we should use this instead.
 * Added CFLAGS for Krait and Scorpion after the cleanup.

Change-Id: Iafb40ecefa353a1169c22601be4ce80069c3f587

Conflicts:
	core/combo/arch/arm/armv7-a-neon.mk

PS6:Use -mcpu=cortex-a15 for krait

Based on https://android.googlesource.com/platform/build/+/d195c6d14e027f12f63508afed245a1ce469c936

Change-Id: Ib409c915c5302cdb44d49978456b7d1cc6a2a250
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>

Ps7:fix
Allow prebuild APK's in Vendor

Change-Id: I361c32fac1e003ec985ffe2282bf8ef922b11ac0