add Makefile rule for test program CREATE_STD_THREADS

Effectively removes -lpthreads from linux/gcc build of test programs in test/api/multithreaded. This was done due to that combination causing a test program to hang due, likely due to an issue with gcc linker and libstdc++ conflicting pthreads code in test program and pthread used by lldb.  Issue has been documented at:
http://llvm.org/bugs/show_bug.cgi?id=21553

Differential Revision: http://reviews.llvm.org/D5838

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@222031 91177308-0d34-0410-b5e6-96231b3b80d8