github: Display meson test logs on failure

Currently the way we integrate the existing tests into meson means meson
test itself doesn't show any detailed logs of the failures, those just go
to the meson testlog file.  As a hack to see what's failing in CI builds,
display that file if the tests fail.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

.github/workflows/build.yml

@@ -62,4 +62,4 @@ jobs:
         run: meson compile -C build
 
       - name: Run check
-        run: meson test -C build
+        run: meson test -C build || cat build/meson-logs/testlog.txt