Add regression test

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 1e10da0..bf40764 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -1948,6 +1948,18 @@
     tests/scripts/depends.py pkalgs
 }
 
+component_build_no_pk_rsa_alt_support () {
+    msg "build: !MBEDTLS_PK_RSA_ALT_SUPPORT" # ~30s
+
+    scripts/config.py full
+    scripts/config.py unset MBEDTLS_PK_RSA_ALT_SUPPORT
+    scripts/config.py set MBEDTLS_RSA_C
+    scripts/config.py set MBEDTLS_X509_CRT_WRITE_C
+
+    # Only compile - this is primarily to test for compile issues
+    make CC=gcc CFLAGS='-Werror -Wall -Wextra -I../tests/include/alt-dummy'
+}
+
 component_build_module_alt () {
     msg "build: MBEDTLS_XXX_ALT" # ~30s
     scripts/config.py full