create libavcodec/sh4 dir when building out-of-tree

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@10171 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -2026,6 +2026,7 @@ if enabled source_path_used; then
          libavcodec/i386 \
          libavcodec/mlib \
          libavcodec/ppc \
+         libavcodec/sh4 \
          libavcodec/sparc \
          libavformat \
          libavutil \