Adjustments for armcc in all.sh

- no HAVE_TIME -> no HAVE_TIME_DATE
- check if --help works, so that the test is cleanly skipped if license server
  cannot be reached
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 6fe6d47..448d519 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -209,7 +209,7 @@
 CC=arm-none-eabi-gcc CFLAGS=-Werror make lib
 fi # arm-gcc
 
-if which armcc >/dev/null; then
+if which armcc >/dev/null && armcc --help >/dev/null; then
 msg "build: armcc, make"
 cleanup
 cp "$CONFIG_H" "$CONFIG_BAK"
@@ -218,6 +218,7 @@
 scripts/config.pl unset MBEDTLS_TIMING_C
 scripts/config.pl unset MBEDTLS_FS_IO
 scripts/config.pl unset MBEDTLS_HAVE_TIME
+scripts/config.pl unset MBEDTLS_HAVE_TIME_DATE
 # following things are not in the default config
 scripts/config.pl unset MBEDTLS_DEPRECATED_WARNING
 scripts/config.pl unset MBEDTLS_HAVEGE_C # depends on timing.c