Make vala C code errors non-fatal #986

Job	Run time
OS (apt-docker.io/amd64/ubuntu:devel)	1m 53s
OS (apt-docker.io/amd64/ubuntu:latest)	2m 13s
OS (apt-docker.io/amd64/ubuntu:rolling)	2m 1s
OS (apt-docker.io/i386/debian:testing)	1m 57s
OS (apt-docker.io/amd64/debian:testing)	1m 55s
OS (dnf-registry.fedoraproject.org/fedora:latest)	3m 15s
OS (dnf-registry.fedoraproject.org/fedora:rawhide)	2m 24s
OS (alpine-docker.io/alpine)	30s
OS (alpine-docker.io/i386/alpine)	29s
OS ([email protected]/alpine)	29s
OS (nix-docker.io/nixos/nix)	59s
OS (gentoo-)	4m 51s
OS (alpine@gudev-alpine, EXTRA_PACKAGES=libgudev-dev)	42s
	23m 38s

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