Fix buildbot failure due to triple normalization issues

We have been seeing buildbot failures due to #122629
I posted #135571 to update the
triple normalization logic, but that patch hasn't gotten any traction.

So in this patch I am updating the lit config to use triple from clang's
output for `%itanium_abi_triple` substitution, instead of relying on
`self.config.target_triple` which might not be in a canonical form.

Buildbot failure example: https://lab.llvm.org/buildbot/#/builders/40

Change-Id: Ib9c3425fddac45d7468fad20929fd29358a55e1b

Author: UsmanNadeem

llvm/utils/lit/lit/llvm/config.py

@@ -674,7 +674,11 @@ def use_clang(
                 (
                     "%itanium_abi_triple",
                     self.normalize_triple(
-                        self.make_itanium_abi_triple(self.config.target_triple)
+                        self.make_itanium_abi_triple(
+                            self.get_process_output(
+                                [self.config.clang, "--print-target-triple"]
+                            )[0].split("\n")[0]
+                        )
                     ),
                 )
             )