Modify llvm-ar and llvm-ranlib to use the actual name of the executable
when printing the usage text via the '--help' flag.
Reviewers: Maskray, jhenderson, gbreynoo
Differential Revision: https://reviews.llvm.org/D124445
If llvm-ar is installed at arm-pokymllib32-linux-gnueabi-llvm-ar, it may
think it is llvm-lib due to the "lib" substring.
Improve the heuristic to make all the following work as intended:
llvm-ar-9 (llvm-9 package on Debian)
llvm-ranlib.exe
Lib.exe (reported by D44808)
arm-pokymllib32-linux-gnueabi-llvm-ar (reported by D71030)
Reviewed By: raj.khem, rupprecht
Differential Revision: https://reviews.llvm.org/D71302
Chris Jackson