Add tests directory to file copying to resolve Makefile dependency

Author: oysteinkrog

mingw-build/PKGBUILD

@@ -73,7 +73,7 @@ prepare() {
   cd "${startdir}/.."
   # Copy all files except build directory and .git
   find . -maxdepth 1 -type f -exec cp {} "${srcdir}/${_realname}/" \;
-  for dir in compat doc ffbuild fftools libav* libsw* tools; do
+  for dir in compat doc ffbuild fftools libav* libsw* tests tools; do
     if [ -d "$dir" ]; then
       cp -r "$dir" "${srcdir}/${_realname}/" 2>/dev/null || true
     fi