Revert "Revert "And so begins the LTO experiment...""

This reverts commit dacfc5a3dd0b9b7dccc0168c40693430bca8437f.
Revert "Revert "This is not the flag you are looking for...""

This reverts commit 51bae022650e31a58ce9db230cd96fcba224e60e.
Revert "Revert "Handle LTO like how AOSP handles FDO.""

This reverts commit bdac8cd0002087c3610c4c39686778d984a26e85.
[test] pass TARGET_THUMB_STRICT and -O3 to clang

clang is used to compile mostly graphics related code in 4.4.X.
Upstream is moving to replace GCC with a newer clang/llvm, so we
should start getting familiar with it.. and perhaps switch to a
newer drop-in prebuilt with polly support soon

-VanirAOSP

Change-Id: Ic8eb6be6ba3a9cd472a4ec9c34c515c1f25d167e