third_party/libcxxabi: Add test suite (#1076)

Added the `libcxxabi` test suite as found in LLVM 17.0.6.

Some tests that do not apply to the current configuration of
comsopolitan are not added. These include:
- `backtrace_test`, `forced_unwind*`: Use unwind function unsupported in
SjLj mode.
- `noexception*`: Designed to test `libcxxabi` in no exceptions mode.

Some tests are added but not enabled due to bugs specific to GCC or
cosmopolitan. These are clearly indicated in the `BUILD.mk` file.

third_party/libcxxabi/test/catch_function_02.pass.cc

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Can you have a catch clause of array type that catches anything?
+// UNSUPPORTED: no-exceptions
+
+#include "third_party/libcxx/cassert"
+
+void f() {}
+
+int main(int, char**)
+{
+    typedef void Function();
+    try
+    {
+        throw f;     // converts to void (*)()
+        assert(false);
+    }
+    catch (Function b)  // equivalent to void (*)()
+    {
+    }
+    catch (...)
+    {
+        assert(false);
+    }
+
+    return 0;
+}