fix build break with linaro 4.7.3 toolchain

Change-Id: Ideda40cadcff4bad73e741ffd17b130d83c952ba
Compiler flags

Change-Id: Ia201e4c43d93a811ab84cf926acb0f76e632121b
ccache

Change-Id: I5d93c2f0d08ce6b671752ec27a39f0c33918973e
add -pipe flag

Change-Id: I9eab875c63f84c5f1faddd7dfa62d78747a9ecae