crt: testcases: Fix passing -municode for the t__wstat_all testcase

Signed-off-by: Martin Storsjö <martin@martin.st>
diff --git a/mingw-w64-crt/Makefile.am b/mingw-w64-crt/Makefile.am
index 7a986d5..7f79834 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -4471,7 +4471,7 @@
   testcase_progs += testcases/t_municode testcases/t_tmain testcases/t__wstat_all
   testcases_t_municode_CFLAGS = -municode
   testcases_t_tmain_CFLAGS = -municode -D_UNICODE
-  testcases_t__wstat_all = -municode
+  testcases_t__wstat_all_CFLAGS = -municode
 endif
 
 # Do not specify TESTS = check_PROGRAMS, because some TESTS