gitlab#205 - configure.ac: Check the minimum version of rustc (1.20)

GNOME/librsvg#205
3 jobs for <span class="ref-name">check-rustc-version</span> in 4 minutes and 11 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #9352
fedora:test

00:04:11

 
  Lint
manual #9354
allowed to fail manual
clippy
manual #9353
allowed to fail manual
rustfmt