[libc++] Mark a test relying on typeid as unsupported without RTTI.

(cherry picked from commit f50cad2)

Author: var-const

libcxx/test/libcxx/utilities/exception_guard.odr.sh.cpp

@@ -6,6 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+// This test relies on `typeid` and thus requires `-frtti`.
+// UNSUPPORTED: no-rtti
+
 // Make sure that we don't get ODR violations with __exception_guard when
 // linking together TUs compiled with different values of -f[no-]exceptions.