BUILD: Makefile: error when trying to build with aws-lc with the wrong flags

BUILD: Makefile: error when trying to build with aws-lc with the wrong flags

USE_OPENSSL_AWSLC=1 is required when trying to build with aws-lc. This
was already required before, but kind of worked without it since
f76e8e50f460 ("BUILD: ssl: replace USE_OPENSSL_AWSLC by
OPENSSL_IS_AWSLC").

However since 9ac590b5 ("MEDIUM: ssl: introduce src/fips.c with TLS
version check"), this can't work by accident anymore.

This patch emits an error when we find OPENSSL_IS_AWSLC, but we didn't
found USE_OPENSSL_AWSLC=1.