build_llvm_release.bat: add tarball export to x64 release (#79840)
Like linux releases, export a tar.xz files containing most llvm tools,
including non toolchain utilities, llvm-config, llvm-link and others.
We do this by reconfiguring cmake one last time at the last step,
running the install target so we do not need to recompile anything.
Fix #51192
Fix #53052