clang:try Ofast in replacement with O3, also enabled munaligned-access and ensured vectorization is enabled

This might cause instability because Ofast enables ffast-math that may break floating point standard

Change-Id: Iaf012c9396fea51c6d3eda50695c4479de3eb712

Conflicts:
	core/clang/config.mk

clang:try Ofast in replacement with O3, also enabled munaligned-access and ensured vectorization is enabled

This might cause instability because Ofast enables ffast-math that may break floating point standard

Change-Id: Iaf012c9396fea51c6d3eda50695c4479de3eb712

Conflicts:
	core/clang/config.mk
Revert "clang:substitute -mfpu=neon-vfpv4 for -mfpu=neon"

This reverts commit bf86d7bbdd88d3f0db2e45a66c8e4c7650601378.

Revert "clang:substitute -mfpu=neon-vfpv4 for -mfpu=neon"

This reverts commit bf86d7bbdd88d3f0db2e45a66c8e4c7650601378.
-mtune=cortex flag