build: add local patching support to our external dependencies

configure.py

@@ -345,7 +345,7 @@ def _download_extract(args, dep_item):
         logging.info("remove previous %s copy", target)
         _rmtree(target)
 
-    # Link (or copy)
+    # Link (or copy) and patch
     if not op.exists(target):
         logging.info("symlink %s -> %s", target, rel_extract_dir)
         try:
@@ -356,6 +356,11 @@ def _download_extract(args, dep_item):
             logging.info("unable to symlink, fallback on copy (%s -> %s)", extract_dir, target)
             shutil.copytree(extract_dir, target)
 
+        patch_basedir = op.join(_ROOTDIR, "patches", name)
+        for patch in dep.get("patches", []):
+            patch_path = op.join(patch_basedir, patch)
+            run(["patch", "-p1", "-i", patch_path], cwd=target)
+
     return name, target