add POSIX macros check and fallback

Author: yiwu0b11

flang/runtime/extensions.cpp

@@ -23,12 +23,19 @@ inline void ctime_alloc(char *buffer, size_t bufsize, const time_t cur_time,
   int error = ctime_s(buffer, bufsize, &cur_time);
   RUNTIME_CHECK(terminator, error == 0);
 }
-#else
+#elif _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE || _SVID_SOURCE || \
+    _POSIX_SOURCE
 inline void ctime_alloc(char *buffer, size_t bufsize, const time_t cur_time,
     Fortran::runtime::Terminator terminator) {
   const char *res = ctime_r(&cur_time, buffer);
   RUNTIME_CHECK(terminator, res != nullptr);
 }
+#else
+inline void ctime_alloc(char *buffer, size_t bufsize, const time_t cur_time,
+    Fortran::runtime::Terminator terminator) {
+  buffer[0] = '\0';
+  terminator.Crash("fdate is not supported.");
+}
 #endif
 
 extern "C" {