Make the triple an explicit argument of FindTargetProgramPath.

Make the triple an explicit argument of FindTargetProgramPath.
Preserve the original triple in the NetBSD toolchain when using -m32 or
-m64 and the resulting effective target is different from the triple it
started with. This allows -m32 to use the same assembler/linking in
cross-compiling mode and avoids confusion about passing down target
specific flags in that case like --32.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@131404 91177308-0d34-0410-b5e6-96231b3b80d8