build_ios_libs.sh: Add command line bitcode option.
build_ios_libs.sh: Add command line bitcode option.

BUG=webrtc:5085
NOTRY=True

Review-Url: https://codereview.webrtc.org/2523623002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#15175}

ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc