Fixes build configuration for armcc test build in all.sh

In the test script tests/scripts/all.sh the armcc build is a baremetal build
and doesn't use MBEDTLS_HAVE_TIME therefore the test configuration
MBEDTLS_PLATFORM_TIME_ALT which is dependent on it must be unset.
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 22137cd..be32dce 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -338,6 +338,7 @@
 scripts/config.pl unset MBEDTLS_THREADING_C
 scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # execinfo.h
 scripts/config.pl unset MBEDTLS_MEMORY_BUFFER_ALLOC_C # calls exit
+scripts/config.pl unset MBEDTLS_PLATFORM_TIME_ALT # depends on MBEDTLS_HAVE_TIME
 CC=armcc AR=armar WARNING_CFLAGS= make lib
 fi # armcc