[libc] Relocate the closing directive of #ifdef

Changed where an #endif was placed because previously it
prevented three macro definitions from being enable in Windows.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D106087

libc/utils/UnitTest/LibcTest.h

@@ -380,12 +380,12 @@ template <typename... Types> using TypeList = internal::TypeList<Types...>;
   if (!EXPECT_DEATH(FUNC, EXIT))                                               \
   return
 
+#endif // ENABLE_SUBPROCESS_TESTS
+
 #define __CAT1(a, b) a##b
 #define __CAT(a, b) __CAT1(a, b)
 #define UNIQUE_VAR(prefix) __CAT(prefix, __LINE__)
 
-#endif // ENABLE_SUBPROCESS_TESTS
-
 #define EXPECT_THAT(MATCH, MATCHER)                                            \
   do {                                                                         \
     auto UNIQUE_VAR(__matcher) = (MATCHER);                                    \