Build ninja statically when using musl

The aosp-llvm-toolchain build uses LD_LIBRARY_PATH to affect the
processes run inside ninja, but that affects ninja too.  There's
no way to use a different LD_LIBRARY_PATH for ninja and its
subprocesses, so just make ninja static instead.

Bug: 190084016
Test: aosp-build-tools linux_musl build
Change-Id: Ifd6d871ccb973f97eab76cd9ada58df1af175d9f
1 file changed