[test-release.sh] Respect the given width in LIT runs by adding `-j` in LLVM_LIT_ARGS.

This patch adds allows the LIT runs within test-release.sh to obey the width that
is passed into the script. This is accomplished by adding the width in the LLVM_LIT_ARGS
CMake configuration.

Differential Revision: https://reviews.llvm.org/D115350