[TestGlobalVariables] LD_LIBRARY_PATH should be process working directory.

Summary:
The inferior can load the library now, but the remote test is still failing
because of a module loading problem in LLDB.

Reviewers: ovyalov, sivachandra, clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D8038

llvm-svn: 231120