[librsvg: 2/3] ci: turn rustc warnings into errors in the CI

[Sven Neumann <sneumann src gnome org>]

commit 2ddf50185bcd8eb60c44e32d3acde7945050371e
Author: Jordan Petridis <jpetridis gnome org>
Date:   Tue Nov 3 19:50:42 2020 +0200

    ci: turn rustc warnings into errors in the CI
    
    followup of !431 [1]
    
    deny(warnings) is an anti-pattern as a newer release of
    the compiler can cause working/released builds to stop
    compilling for downstreams.
    
    Having to export a RUST_FLAG is not the prettiest, but
    its the best we got atm [2]
    
    [1] https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/431
    [2] https://github.com/rust-lang/cargo/issues/3591

 .gitlab-ci.yml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b59b50e4..78755545 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -8,6 +8,8 @@ variables:
   AMD64_DEBIAN_TESTING:      "registry.gitlab.gnome.org/gnome/librsvg-oci-images/amd64/debian:testing"
 
   LIBRSVG_DEBUG: "yes"
+  # Turn compiler warnings into errors
+  RUSTFLAGS: '-D warnings'
 
 image: $AMD64_OPENSUSE_TUMBLEWEED