add PATCH dir

Author: TNTPro

env.source

@@ -17,6 +17,7 @@ else
   TARGET_DIR="${TARGET_DIR:-$ENV_ROOT/target}"
   DOWNLOAD_DIR="${DOWNLOAD_DIR:-$ENV_ROOT/dl}"
   BIN_DIR="${BIN_DIR:-$ENV_ROOT/bin}"
+  PATCH_DIR="${PATCH_DIR:-$ENV_ROOT/patches}"
 
   export LDFLAGS="-L${TARGET_DIR}/lib"
   # FIXME: detect OS somehow