gdb/testsuite: skip gdb.threads/omp-par-scope.exp with clang

Since 2020 it has been reported to clang[1] that the debug information
around OpenMP is insufficient.  The OpenMP section is not declared
within the correct scope, and instead clang marks as if the section was
a function in the global scope.  This causes several failures in the
test gdb.threads/omp-par-scope.exp when using clang to test GDB.

Since this isn't a true failure of GDB, and there is little expectation
that clang will be able to fix this soon, this commit disables the
aforementioned test when clang is being used.

[1] https://github.com/llvm/llvm-project/issues/44236

Approved-by: Kevin Buettner <kevinb@redhat.com>

gdb/testsuite/gdb.threads/omp-par-scope.exp

@@ -20,6 +20,14 @@
 
 standard_testfile
 
+if { [test_compiler_info "clang*"] } {
+    # Clang doesn't add OpenMP information in the correct scope,
+    # so all relevant tests here will fail.  See here for more info:
+    # https://github.com/llvm/llvm-project/issues/44236
+    unsupported "Clang doesn't provide required info for the test"
+    return
+}
+
 set have_nested_function_support 0
 set opts {openmp debug}
 if [support_nested_function_tests] {