[HIP] Use argv[0] as the default choice for the Executable name.

The path produced by getMainExecutable() may not be the right one when the files are installed in
a symlinked tree and when the real location of llvm-objdump is in a different directory.

Given that clang-offload-bundler is invoked by clang, the driver already does the job figuring out
the right path (e.g. it pays attention to -no-canonical-prefixes).
Offload bundler should use it, instead of trying to figure out the path on its
own.

Differential Revision: https://reviews.llvm.org/D90436