hotdoc: fix build with gcc15

- add patch from merged upstream commit:
https://github.com/hotdoc/hotdoc/commit/adf8518431fafb78c9b47862a0a9a58824b6a421

Fixes build failure with gcc15:
```
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l: In function ‘yylex’:
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:49:10:
error: too many arguments to function ‘parse_comment’; expected 0, have 1
   49 | "/*"                            { return parse_comment (comments);}
      |          ^~~~~~~~~~~~~  ~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:37:12: note: declared here
   37 | static int parse_comment ();
      |            ^~~~~~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:50:10:
error: too many arguments to function ‘parse_define’; expected 0, have 1
   50 | {HASH}{SPACE}*"define"{SPACE}*  { return parse_define (comments); }
      |          ^~~~~~~~~~~~  ~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:38:12: note: declared here
   38 | static int parse_define ();
      |            ^~~~~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l: At top level:
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:80:1:
error: conflicting types for ‘parse_define’; have ‘int(PyObject *)’ {aka ‘int(struct _object *)’}
   80 | parse_define (PyObject *comments)
      | ^~~~~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:38:12:
note: previous declaration of ‘parse_define’ with type ‘int(void)’
   38 | static int parse_define ();
      |            ^~~~~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:126:1:
error: conflicting types for ‘parse_comment’; have ‘int(PyObject *)’ {aka ‘int(struct _object *)’}
  126 | parse_comment (PyObject *comments)
      | ^~~~~~~~~~~~~
/build/hotdoc-0.17.4/hotdoc/parsers/c_comment_scanner/scanner.l:37:12:
note: previous declaration of ‘parse_comment’ with type ‘int(void)’
   37 | static int parse_comment ();
      |            ^~~~~~~~~~~~~
```

pkgs/development/tools/hotdoc/default.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   buildPythonApplication,
+  fetchpatch,
   fetchPypi,
   replaceVars,
   clang,
@@ -45,6 +46,13 @@ buildPythonApplication rec {
       clang = lib.getExe clang;
       libclang = "${lib.getLib libclang}/lib/libclang${stdenv.hostPlatform.extensions.sharedLibrary}";
     })
+
+    # Fix build with gcc15
+    (fetchpatch {
+      name = "hotdoc-fix-c_comment_scanner-function-prototypes-gcc15.patch";
+      url = "https://github.com/hotdoc/hotdoc/commit/adf8518431fafb78c9b47862a0a9a58824b6a421.patch";
+      hash = "sha256-5y50Yk+AjV3aSk8H3k9od/Yvy09FyQQOcVOAcstQnw8=";
+    })
   ];
 
   build-system = [ setuptools ];