zeroc-ice: 2.7.3 -> 2.7.2.20

As reported in
https://github.com/NixOS/nixpkgs/pull/475929#issuecomment-4671420403,
2.7.3 is nowhere to be found / has been scrubbed upstream.

We're only still able to build this because the FOD is in
cache.nixos.org.

Meanwhile 2.7.2.20 has been tagged however, and it has the patches from
https://github.com/zeroc-ice/mcpp/pull/12 merged, so let's update our
derivation to that.

We still keep an empty `patches = []` around, as we still don't want to
use the patches from the non-forked mcpp.

(cherry picked from commit e49bc27926)

pkgs/by-name/ze/zeroc-ice/fix-mb_init.patch

@@ -1,34 +0,0 @@
-From faa694a7171a06f83034fd869adc4cffa2ae0c18 Mon Sep 17 00:00:00 2001
-From: laurensmiers <laurensmiers@protonmail.com>
-Date: Wed, 22 Oct 2025 14:50:23 +0200
-Subject: [PATCH] fix: mb_init does not accept any parameter
-
-Defined in mbchar.c:114 :
-```c
-void    mb_init()
-/*
- * Initialize multi-byte character settings.
- * First called prior to setting the 'mcpp_mode'.
- * Will be called again each time the multibyte character encoding is changed.
- */
-{
-```
-
-It does not expect any parameters.
----
- mcpp_main.c | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
-
-diff --git a/mcpp_main.c b/mcpp_main.c
-index 54a62b2..44265ad 100644
---- a/mcpp_main.c
-+++ b/mcpp_main.c
-@@ -302,7 +302,7 @@ int     mcpp_lib_main
-     inc_dirp = &null;   /* Initialize to current (null) directory   */
-     cur_fname = cur_fullname = "(predefined)";  /* For predefined macros    */
-     init_defines();                         /* Predefine macros     */
--    mb_init(TRUE);      /* Should be initialized prior to get options   */
-+    mb_init();      /* Should be initialized prior to get options   */
-     do_options( argc, argv, &in_file, &out_file);   /* Command line options */
- 
-     /* Open input file, "-" means stdin.    */

pkgs/by-name/ze/zeroc-ice/fix-reserved-keywords.patch

@@ -1,55 +0,0 @@
-From bd5ddbde9e4ed24101cdc86007f26e95f38dd5b1 Mon Sep 17 00:00:00 2001
-From: laurensmiers <laurensmiers@protonmail.com>
-Date: Wed, 22 Oct 2025 14:52:30 +0200
-Subject: [PATCH] fix: don't use reserved keyword for goto statement
-
-Rename:
-- 'true' to 'exit_success'
-- 'false' to 'exit_fail'
-
-Chose not to change the flow of the code by removing the goto's to
-avoid regressions.
----
- system.c | 10 +++++-----
- 1 file changed, 5 insertions(+), 5 deletions(-)
-
-diff --git a/system.c b/system.c
-index 646caf6..0a15aec 100644
---- a/system.c
-+++ b/system.c
-@@ -1738,7 +1738,7 @@ static int  open_file(
-     if (! fullname)                 /* Non-existent or directory    */
-         return  FALSE;
-     if (included( fullname))        /* Once included    */
--        goto  true;
-+        goto  exit_success;
- 
-     if ((max_open != 0 && max_open <= include_nest)
-                             /* Exceed the known limit of open files */
-@@ -1765,12 +1765,12 @@ static int  open_file(
-         if ((fp = mcpp_fopen( fullname, "r")) == NULL) {
-             file->fp = mcpp_fopen( cur_fullname, "r");
-             fseek( file->fp, file->pos, SEEK_SET);
--            goto  false;
-+            goto  exit_fail;
-         }
-         if (max_open == 0)      /* Remember the limit of the system */
-             max_open = include_nest;
-     } else if (fp == NULL)                  /* No read permission   */
--        goto  false;
-+        goto  exit_fail;
-     /* Truncate buffer of the includer to save memory   */
-     len = (int) (file->bptr - file->buffer);
-     if (len) {
-@@ -1802,9 +1802,9 @@ static int  open_file(
-     if (mkdep && ((mkdep & MD_SYSHEADER) || ! infile->sys_header))
-         put_depend( fullname);          /* Output dependency line   */
- 
--true:
-+exit_success:
-     return  TRUE;
--false:
-+exit_fail:
-     free( fullname);
-     return  FALSE;
- }

pkgs/by-name/ze/zeroc-ice/package.nix

@@ -16,21 +16,17 @@
 let
   mcpp' = mcpp.overrideAttrs (prevAttrs: rec {
     pname = "mcpp-zeroc-ice";
-    version = "2.7.3";
+    version = "2.7.2.20";
 
     src = fetchFromGitHub {
       owner = "zeroc-ice";
       repo = "mcpp";
       rev = "v${version}";
-      hash = "sha256-hZGU5mqMRTTHV2bR9uzM6ALj1sypjPxO5Ajg8aKzLxc=";
+      hash = "sha256-FlzHpfYoHzbz5DfXgkr6Hf96xejRKd0Rr1TmzE5GyGg=";
     };
 
     # zeroc-ice's fork diverges quite a bit from upstream mcpp, so prevAttrs.patches is not used here
-    patches = [
-      # See https://github.com/zeroc-ice/mcpp/pull/12
-      ./fix-mb_init.patch
-      ./fix-reserved-keywords.patch
-    ];
+    patches = [ ];
 
     installFlags = prevAttrs.installFlags or [ ] ++ [ "PREFIX=$(out)" ];
   });