dfsan: Fix test with gcc 15.

With gcc 15 we end up emitting a reference to the
std::__glibcxx_assert_fail function because of this change:
gcc-mirror/gcc@361d230
combined with assertion checks in the std::atomic implementation.

This reference is undefined with dfsan causing the test to fail. Fix it
by defining the macro that disables assertions.

Pull Request: #153873

Author: pcc

compiler-rt/test/dfsan/atomic.cpp

@@ -1,9 +1,12 @@
-// RUN: %clangxx_dfsan %s -fno-exceptions -o %t && %run %t
-// RUN: %clangxx_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 %s -fno-exceptions -o %t && %run %t
+// RUN: %clangxx_dfsan %s -fno-exceptions -D_GLIBCXX_NO_ASSERTIONS -o %t && %run %t
+// RUN: %clangxx_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 %s -fno-exceptions -D_GLIBCXX_NO_ASSERTIONS -o %t && %run %t
 //
 // Use -fno-exceptions to turn off exceptions to avoid instrumenting
 // __cxa_begin_catch, std::terminate and __gxx_personality_v0.
 //
+// Use -D_GLIBCXX_NO_ASSERTIONS to avoid depending on
+// std::__glibcxx_assert_fail with gcc >= 15.
+//
 // TODO: Support builtin atomics. For example, https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html
 // DFSan instrumentation pass cannot identify builtin callsites yet.