[runtimes] Don't depend on libpthread on Android

r362048 added support for ELF dependent libraries, but broke Android
build since Android does not have libpthread. Remove the dependency on
the Android build.

Differential Revision: https://reviews.llvm.org/D65098

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@366734 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed