[hwasan] Link ubsan_cxx to shared runtime library.

[eugenis]

Summary

This is needed for C++-specific ubsan and cfi error reporting to work.

[vitalybuka]

LGTM

compiler-rt/lib/hwasan/CMakeLists.txt

add_compiler_rt_runtime(clang_rt.hwasan
     OBJECT_LIBS
             RTHwasan_dynamic
             RTInterception
             RTSanitizerCommon
             RTSanitizerCommonLibc
             RTSanitizerCommonCoverage
             RTSanitizerCommonSymbolizer
             RTUbsan
+            RTUbsan_cxx
             # The only purpose of RTHWAsan_dynamic_version_script_dummy is to
             # carry a dependency of the shared runtime on the version script.
             # Replacing it with a straightforward
             # add_dependencies(clang_rt.asan-dynamic-${arch} clang_rt.asan-dynamic-${arch}-version-list)
             # generates an order-only dependency in ninja.
             RTHwasan_dynamic_version_script_dummy
     CFLAGS ${HWASAN_DYNAMIC_CFLAGS}
     LINK_FLAGS ${HWASAN_DYNAMIC_LINK_FLAGS}

compiler-rt/test/hwasan/TestCases/cfi.cc

+// RUN: %clang_hwasan -fsanitize=cfi -fno-sanitize-trap=cfi -flto -fvisibility=hidden -fuse-ld=lld %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+// REQUIRES: android
+
+// Smoke test for CFI + HWASAN.
+
+struct A {
+  virtual void f();
+};
+
+void A::f() {}
+
+int main() {
+  // CHECK: control flow integrity check for type {{.*}} failed during cast to unrelated type
+  A *a = reinterpret_cast<A *>(reinterpret_cast<void *>(&main));
+  (void)a;
+}