Work around clang 3.8 bug

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 6ce8e93..06ef19c 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -4994,11 +4994,15 @@
 }
 
 component_test_block_cipher_no_decrypt_aesni () {
+    # This consistently causes an llvm crash on clang 3.8, so use gcc
+    export CC=gcc
     config_block_cipher_no_decrypt 0
     common_block_cipher_no_decrypt
 }
 
 component_test_block_cipher_no_decrypt_aesni_use_psa () {
+    # This consistently causes an llvm crash on clang 3.8, so use gcc
+    export CC=gcc
     config_block_cipher_no_decrypt 1
     common_block_cipher_no_decrypt
 }