Rename llvm library from libLLVM-X.Y to libLLVM-X
As we are only doing X.0.Z releases (not using the minor version), there is no need to keep -X.Y in the version.
Like patch https://reviews.llvm.org/D41808, I propose that we rename libLLVM-7.0svn.so to libLLVM-7svn.so
This patch will also rename downstream libraries like liblldb-7.0 to liblldb-7
Reviewers: axw, beanz, dim, hans
Reviewed By: dim, hans
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D41869