[CI] Reset all submodules so we can apply the patches.

.gitlab-ci.yml

@@ -9,6 +9,8 @@ before_script:
 - git submodule sync --recursive
 - git submodule update --init --recursive
 # end workaround
+# make sure we can apply the patches
+- git submodule foreach --recursive git reset --hard HEAD
 - ( cd python/loopy && git apply ../../patches/loopy/*.patch )
 - ( cd dune/perftool/vectorclass && git apply ../../../patches/vectorclass/*.patch )