Support building build tools against musl

Add --musl argument to enable building against musl.

Bug: 190084016
Test: build-prebuilts.sh
Test: build-prebuitls.sh --musl
Test: build-prebuilts.sh --musl --resume
Change-Id: I5fa2a074a6e36f7742be943b05121a634bc4aeba
1 file changed