container: Install openssl-devel in build stage

The OpenID Connect integration introduced a dependency on the system
OpenSSL library.  As such, the OpenSSL development package needs ot be
available when building the application.

Containerfile

@@ -6,6 +6,7 @@ RUN --mount=type=cache,target=/var/cache \
 		cargo \
 		libvirt-devel \
 		rust \
+		openssl-devel \
 	&& :
 
 COPY . /build