Additionally fix the copy if enabled on multi-config targets.
Summary:
This changes the copy command for libomp.so to use the output of the target as
the source of the copy, rather than trying to find it based on
${LIBOMP_LIBRARY_DIR}, which appears to be incorrect in multi-config generator
builds.
Reviewers: jdoerfert
Subscribers: mgorny, yaxunl, guansong, sstefan1, openmp-commits
Tags: #openmp
Differential Revision: https://reviews.llvm.org/D84148