[Driver] Drop $DEFAULT_TRIPLE-$name as a fallback program name

D13340 introduced this behavior which is not needed even for mips.
This was raised on https://lists.llvm.org/pipermail/cfe-dev/2020-May/065437.html
but no action was taken.

This was raised again in https://lists.llvm.org/pipermail/cfe-dev/2021-April/067974.html
"The LLVM host/target TRIPLE padding drama on Debian"
as it caused confusion. This patch drops the behavior.

Differential Revision: https://reviews.llvm.org/D99996

GitOrigin-RevId: 8ac5e440615dd3dc9fd2eb88c0bad32fdc5f678c
2 files changed