[libc++] tests with picolibc: xfail one remaining test

Author: domin144

libcxx/test/std/language.support/support.start.term/quick_exit.pass.cpp

@@ -17,6 +17,9 @@
 
 // test quick_exit and at_quick_exit
 
+// TODO: Find out why the at_quick_exit symbol is not found.
+// XFAIL: LIBCXX-PICOLIBC-FIXME
+
 #include <cstdlib>
 
 void f() {}