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_03.pass.cc

@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 a noexcept function pointer be caught by a non-noexcept catch clause?
+// UNSUPPORTED: c++03, c++11, c++14
+// UNSUPPORTED: no-exceptions
+
+// Support for catching a function pointer including noexcept was shipped in macOS 10.13
+// XFAIL: stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{9|10|11|12}}
+
+#include "third_party/libcxx/cassert"
+
+template<bool Noexcept> void f() noexcept(Noexcept) {}
+template<bool Noexcept> using FnType = void() noexcept(Noexcept);
+
+template<bool ThrowNoexcept, bool CatchNoexcept>
+void check()
+{
+    try
+    {
+        auto *p = f<ThrowNoexcept>;
+        throw p;
+        assert(false);
+    }
+    catch (FnType<CatchNoexcept> *p)
+    {
+        assert(ThrowNoexcept || !CatchNoexcept);
+        assert(p == &f<ThrowNoexcept>);
+    }
+    catch (...)
+    {
+        assert(!ThrowNoexcept && CatchNoexcept);
+    }
+}
+
+void check_deep() {
+    auto *p = f<true>;
+    try
+    {
+        throw &p;
+    }
+    catch (FnType<false> **q)
+    {
+        assert(false);
+    }
+    catch (FnType<true> **q)
+    {
+    }
+    catch (...)
+    {
+        assert(false);
+    }
+}
+
+int main(int, char**)
+{
+    check<false, false>();
+    check<false, true>();
+    check<true, false>();
+    check<true, true>();
+    check_deep();
+
+    return 0;
+}