ci: unconditionally turn on -Werror

Closes: #971
Approved by: cgwalters

ci/build-check.sh

@@ -16,9 +16,9 @@ fi
 
 if test -x /usr/bin/clang; then
     git clean -dfx && git submodule foreach git clean -dfx
-    # And now a clang build to find unused variables; perhaps
-    # in the future these could parallelize
+    # And now a clang build to find unused variables because it does a better
+    # job than gcc for vars with cleanups; perhaps in the future these could
+    # parallelize
     export CC=clang
-    export CFLAGS='-Werror=unused-variable'
     build
 fi

ci/build.sh

@@ -12,6 +12,9 @@ pkg_install sudo which attr fuse \
     elfutils
 pkg_install_if_os fedora gjs gnome-desktop-testing parallel coccinelle clang
 
+# always fail on warnings; https://github.com/ostreedev/ostree/pull/971
+export CFLAGS="-Werror ${CFLAGS:-}"
+
 DETECTED_CONFIGOPTS=
 if test -x /usr/bin/gnome-desktop-testing-runner; then
     DETECTED_CONFIGOPTS="${DETECTED_CONFIGOPTS} --enable-installed-tests=exclusive"