[test] llvm-ar: Fix inadvertent unXFAIL for Apple platforms

The history of these XFAILs is clouded. Initially added as target-based
checks in
llvm@629273e
for somewhat vague reasons, soon after switched to host-based checks in
llvm@20b2cd3
"due to the problem being related to the darwin host and not the
target", and recently reverted back to target-based in
llvm#130144 because, to my
understanding, the tests can unexpectedly pass on arm64 macOS with
`llvm-ar` cross-compiled to baremetal arm64.

Anyway, the problem with the current `target={{.*}}-darwin{{.*}}` is
that the Swift build script uses Apple platform names like 'macosx', not
'darwin', for the LLVM target triple, e.g. `arm64-apple-macosx13.0`.

Author: AnthonyLatsis

llvm/test/tools/llvm-ar/extract.test

@@ -1,5 +1,5 @@
 ## Test extract operation.
-# XFAIL: target={{.*}}-darwin{{.*}}
+# XFAIL: target={{.*}}-apple-{{.*}}
 
 # RUN: rm -rf %t && mkdir -p %t/extracted/
 

llvm/test/tools/llvm-ar/print.test

@@ -1,5 +1,5 @@
 ## Test Print output
-# XFAIL: target={{.*}}-darwin{{.*}}
+# XFAIL: target={{.*}}-apple-{{.*}}
 
 # RUN: rm -rf %t && mkdir -p %t
 # RUN: echo file1 > %t/1.txt