[libc++abi] Change LIBCXXABI_NO_TIMER to LIBCXXABI_USE_TIMER

Instead of always defining LIBCXXABI_NO_TIMER to run the tests, only
define LIBCXXABI_USE_TIMER when we want to enable the timer. This makes
the libc++abi testing configuration simpler.

As a fly-by fix, remove the unused LIBUNWIND_NO_TIMER macro from libunwind.

Differential Revision: https://reviews.llvm.org/D111667

GitOrigin-RevId: df3de7647e034797ae3c965d6737bc0a4bc7a779
diff --git a/test/libunwind/test/config.py b/test/libunwind/test/config.py
index 2aa3b82..87a810b 100644
--- a/test/libunwind/test/config.py
+++ b/test/libunwind/test/config.py
@@ -39,7 +39,6 @@
             self.config.available_features.add('libunwind-arm-ehabi')
 
     def configure_compile_flags(self):
-        self.cxx.compile_flags += ['-DLIBUNWIND_NO_TIMER']
         # Stack unwinding tests need unwinding tables and these are not
         # generated by default on all Targets.
         self.cxx.compile_flags += ['-funwind-tables']