Fix TypeError when trying to add a sourceMappingURL section to a WASM file (#22214)

This pull request fixes issue #22213.

Author: sterzy

tools/wasm-sourcemap.py

@@ -140,7 +140,7 @@ def encode_uint_var(n):
 def append_source_mapping(wasm, url):
   logger.debug('Append sourceMappingURL section')
   section_name = "sourceMappingURL"
-  section_content = encode_uint_var(len(section_name)) + section_name + encode_uint_var(len(url)) + url
+  section_content = encode_uint_var(len(section_name)) + section_name.encode() + encode_uint_var(len(url)) + url.encode()
   return wasm + encode_uint_var(0) + encode_uint_var(len(section_content)) + section_content