[libc] disable syscall test without fullbuild

Our syscall implementation depends on a specific macro that's only
defined in our headers. If we're not using our headers, then the test
doesn't work. I've disabled the test in this case because there's no
point in testing the system libc's syscall implementation.

Differential Revision: https://reviews.llvm.org/D134994

GitOrigin-RevId: dbca7b4b2e6329fea90f9af7653fa0df977f0d77
1 file changed