Force software rendering during tests

Workaround for Mesa regression #1025312. We expect only software
rendering to be available in a buildd or autopkgtest environment anyway.

debian/tests/build

@@ -10,6 +10,9 @@ set -x
 
 export NO_AT_BRIDGE=1
 
+# Workaround for #1025312
+export LIBGL_ALWAYS_SOFTWARE=1
+
 WORKDIR=$(mktemp -d)
 cleanup () {
     rm -fr "$WORKDIR"

debian/tests/installed-tests

@@ -11,6 +11,9 @@ export GIO_USE_VOLUME_MONITOR=unix
 
 export XDG_RUNTIME_DIR="$AUTOPKGTEST_TMP"
 
+# Workaround for #1025312
+export LIBGL_ALWAYS_SOFTWARE=1
+
 tests=$(gnome-desktop-testing-runner -l gtk+ |
     cut -f1 -d' ' |
     grep -v '^gtk./a11ystate.test$' |

debian/tests/python3-gi

@@ -2,6 +2,9 @@
 
 export NO_AT_BRIDGE=1
 
+# Workaround for #1025312
+export LIBGL_ALWAYS_SOFTWARE=1
+
 xvfb-run -a -s "-screen 0 1024x768x24" \
 python3 <<EOF
 import gi