Revert "Revert "build: Relax Cortex CFLAGS""

This reverts commit d241d579b2cb2d9d461dae9eb98aa8955ed54ca2.
Revert "Possibly fix multi build"

This reverts commit 4dd0066d4286555b71814bf50aca0105c9dc4569.
Revert "Introducing linaro 4.7"

This reverts commit 56a6be9c582d8801edfe52fdbd5a4eaf04bd1f65.
Revert "build/core: Use better default compiler flags"

This reverts commit 1fc11071b8990aaf6d27578a817657edebb61c02.
Some enchance