Move dependency patches from top level into subdir

Good to not clutter the top-level directory.

flake.nix

@@ -163,10 +163,10 @@
             enableLargeConfig = true;
           }).overrideAttrs(o: {
             patches = (o.patches or []) ++ [
-              ./boehmgc-coroutine-sp-fallback.diff
+              ./dep-patches/boehmgc-coroutine-sp-fallback.diff
 
               # https://github.com/ivmai/bdwgc/pull/586
-              ./boehmgc-traceable_allocator-public.diff
+              ./dep-patches/boehmgc-traceable_allocator-public.diff
             ];
           });
 

package.nix

@@ -174,7 +174,6 @@ in {
           ./mk
           (fileset.fileFilter (f: lib.strings.hasPrefix "nix-profile" f.name) ./scripts)
         ] ++ lib.optionals doBuild [
-          ./boehmgc-coroutine-sp-fallback.diff
           ./doc
           ./misc
           ./precompiled-headers.h