[compiler-rt] Explicitly set dependency on libcxx for MemProfUnitTest

MemProfUnitTest now depends on libcxx but the dependency is not
explicitly expressed in build system, causing build races. This patch
addresses this issue.

Differential Revision: https://reviews.llvm.org/D114267

GitOrigin-RevId: 692131f41aa1a8b4e1f7606546d206201ae2e55c
1 file changed