gmtime: Remove special treatment for IAR
Previous commits attempted to use `gmtime_s()` for IAR systems; however,
this attempt depends on the use of C11 extensions which lead to incompatibility
with other pieces of the library, such as the use of `memset()` which is
being deprecated in favor of `memset_s()` in C11.
diff --git a/include/mbedtls/threading.h b/include/mbedtls/threading.h
index 1b13deb..a65eefa 100644
--- a/include/mbedtls/threading.h
+++ b/include/mbedtls/threading.h
@@ -108,7 +108,7 @@
extern mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex;
#endif
#if defined(MBEDTLS_HAVE_TIME_DATE)
-#if !defined(_WIN32) && !defined(__IAR_SYSTEMS_ICC__) && (defined(unix) || \
+#if !defined(_WIN32) && (defined(unix) || \
defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
defined(__MACH__)))
#include <unistd.h>
@@ -120,7 +120,7 @@
*/
extern mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex;
#endif /* !_POSIX_VERSION || 200112L > _POSIX_THREAD_SAFE_FUNCTIONS */
-#endif /* !_WIN32 && !__IAR_SYSTEMS_ICC__ && (unix || __unix || __unix__ ||
+#endif /* !_WIN32 && (unix || __unix || __unix__ ||
* (__APPLE__ && __MACH__)) */
#endif /* MBEDTLS_HAVE_TIME_DATE */
#endif /* MBEDTLS_THREADING_C */