Revert "build/core: Use better default compiler flags"

This reverts commit 9c83953aea1924516c7bbee9c8a481b4c334c0a8.

Conflicts:
	core/combo/select.mk
Option to use Linaro's compiler flags (see 9c83953)

To enable: export USE_LINARO_COMPILER_FLAGS=yes

Set LD flags to something safe by default.

Original commit: https://github.com/pbeeler/android_build/commit/f54beb181365ac0a1659e9404670789c3d81e578