create src dir if not present. Needed for git-revision.h

src/git_revision.sh

@@ -2,6 +2,7 @@
 
 echo "-- Generating header for git hash"
 GIT_HEADER="src/git-revision.h"
+[ -d src ] || mkdir src
 
 GIT_BRANCH=`git rev-parse --abbrev-ref HEAD`