Merge pull request #6883 from valeriosetti/issue6843

Improve X.509 cert writing serial number management

tests/scripts/all.sh

@@ -1768,6 +1768,9 @@ component_test_full_no_deprecated () {
 
     msg "test: make, full_no_deprecated config" # ~ 5s
     make test
+
+    msg "test: ensure that X509 has no direct dependency on BIGNUM_C"
+    not grep mbedtls_mpi library/libmbedx509.a
 }
 
 component_test_full_no_deprecated_deprecated_warning () {