qa/coccinelle: allow to run from non git directory

For example, when I put the contents of a git worktree into
a Docker image for a test build .git will not be a directory
causing the run_check.sh script to fail.

qa/coccinelle/Makefile.am

@@ -15,7 +15,7 @@ struct-flags.cocci:
 	$(srcdir)/struct-flags.py > $(top_builddir)/qa/coccinelle/struct-flags.cocci
 
 check:
-	$(top_srcdir)/qa/coccinelle/run_check.sh
+	TOP_SRCDIR=$(abs_top_srcdir) $(top_srcdir)/qa/coccinelle/run_check.sh
 
 distclean-local:
 	-rm $(top_builddir)/qa/coccinelle/struct-flags.cocci

qa/coccinelle/run_check.sh

@@ -4,6 +4,7 @@ if [ $1 ]; then
 	case $1 in
 	*[ch])
 		LIST=$@;
+		PREFIX=$(git rev-parse --show-toplevel)/
 		;;
         *..*) 
         	LIST=$(git diff --pretty="format:" --name-only $1 | grep -E '[ch]$')
@@ -14,9 +15,12 @@ if [ $1 ]; then
 		PREFIX=$(git rev-parse --show-toplevel)/
 		;;
 	esac
-else
+elif git rev-parse > /dev/null 2>&1; then
 	LIST=$(git ls-tree -r --name-only --full-tree  HEAD src/ | grep -E '*.c$')
 	PREFIX=$(git rev-parse --show-toplevel)/
+elif [ "${TOP_SRCDIR}" != "" ]; then
+	LIST=$(cd ${TOP_SRCDIR} && find src -name \*.[ch])
+	PREFIX=${TOP_SRCDIR}/
 fi
 
 if [ -z "$CONCURRENCY_LEVEL" ]; then
@@ -26,7 +30,7 @@ else
 	echo "Using concurrency level $CONCURRENCY_LEVEL"
 fi
 
-for SMPL in $(git rev-parse --show-toplevel)/qa/coccinelle/*.cocci; do
+for SMPL in ${PREFIX}qa/coccinelle/*.cocci; do
 	echo "Testing cocci file: $SMPL"
 	if command -v parallel >/dev/null; then
 		echo -n $LIST | parallel -d ' ' -j $CONCURRENCY_LEVEL spatch --very-quiet -sp_file $SMPL --undefined UNITTESTS $PREFIX{} || if [ -z "$NOT_TERMINAL" ]; then exit 1; fi