Update to 1.4.21

Author: IsabelParedes

recipes/recipes_emscripten/m4/recipe.yaml

@@ -1,5 +1,5 @@
 context:
-  version: 1.4.19
+  version: 1.4.21
   name: m4
 
 package:
@@ -8,7 +8,7 @@ package:
 
 source:
   url: https://ftp.gnu.org/gnu/m4/m4-${{ version }}.tar.gz
-  sha256: 3be4a26d825ffdfda52a56fc43246456989a3630093cced3fbddf4771ee58a70
+  sha256: 38ae59f7a30bf9c108193cc5c25fbb06014f21e230c7ede2eff614f7b7c37ed8
   patches:
   - patches/obstack_alloc_fail.patch