[clang] [Driver] Fix Arm/AArch64 Link Argument tests (PR #144582)

[Garvit Gupta via cfe-commits]

quic-garvgupt wrote:

`ToolChain::UnwindLibType ToolChain::GetUnwindLibType(
    const ArgList &Args) const {
  if (unwindLibType)
    return *unwindLibType;

  const Arg *A = Args.getLastArg(options::OPT_unwindlib_EQ);
  StringRef LibName = A ? A->getValue() : CLANG_DEFAULT_UNWINDLIB;`
  
  
 
 If --unwindlib= is not set to empty explicitly, then `CLANG_DEFAULT_UNWINDLIB` overrides. I think, adding `--unwindlib=`, might fix the tests.

https://github.com/llvm/llvm-project/pull/144582