libiconv: make default on Darwin

The Darwin libiconv tries to be compatible with GNU libiconv, but it’s
not. Recent versions of Autoconf and gnulib include checks for issues in
Darwin’s libiconv implementation, which has effectively turned
`autoreconfHook` into `autoBreakDarwinHook` due to failing to link
libiconv. Instead of continuing to work around it, make GNU libiconv the
default. With the UTF-8-MAC patch, it should be a drop-in replacement.

Author: reckenrode

pkgs/stdenv/darwin/default.nix

@@ -277,6 +277,7 @@ let
   sdkPackages = prevStage: {
     inherit (prevStage)
       bashNonInteractive
+      libiconvReal
       libpng
       libxml2
       libxo
@@ -291,7 +292,6 @@ let
       Csu
       adv_cmds
       copyfile
-      libiconv
       libresolv
       libsbuf
       libutil
@@ -557,16 +557,16 @@ assert bootstrapTools.passthru.isFromBootstrapFiles or false; # sanity check
         # Use this stage’s CF to build CMake. It’s required but can’t be included in the stdenv.
         cmake = self.cmakeMinimal;
 
-        # Use libiconvReal with gettext to break an infinite recursion.
-        gettext = super.gettext.override { libiconv = super.libiconvReal; };
-
         # Disable grep’s tests for now due to impure locale updates in
         # macOS 15.4 breaking them in the bootstrap.
         gnugrep = super.gnugrep.overrideAttrs { doCheck = false; };
 
         # Disable tests because they use dejagnu, which fails to run.
         libffi = super.libffi.override { doCheck = false; };
 
+        # Avoid an infinite recursion where a stdenv with libiconv is used to build libiconv.
+        libiconvReal = super.libiconvReal.override { stdenv = super.darwin.bootstrapStdenv; };
+
         # Avoid pulling in a full python and its extra dependencies for the llvm/clang builds.
         libxml2 = super.libxml2.override { pythonSupport = false; };
 
@@ -1050,6 +1050,7 @@ assert bootstrapTools.passthru.isFromBootstrapFiles or false; # sanity check
               ld64.lib
               ld64.out
               libffi.out
+              libiconv.out
               libxml2.out
               ncurses.dev
               ncurses.man
@@ -1076,7 +1077,6 @@ assert bootstrapTools.passthru.isFromBootstrapFiles or false; # sanity check
             binutils
             binutils.bintools
             libcxx
-            libiconv.out
             libresolv.out
             libsbuf.out
             libSystem
@@ -1192,8 +1192,8 @@ assert bootstrapTools.passthru.isFromBootstrapFiles or false; # sanity check
     assert isFromNixpkgs prevStage.binutils-unwrapped.src;
     assert isBuiltByNixpkgsCompiler prevStage.curl;
 
-    # libiconv should be an alias for darwin.libiconv
-    assert prevStage.libiconv == prevStage.darwin.libiconv;
+    # libiconv should be an alias for libiconvReal
+    assert prevStage.libiconv == prevStage.libiconvReal;
 
     {
       inherit (prevStage) config overlays stdenv;

pkgs/top-level/all-packages.nix

@@ -6676,8 +6676,6 @@ with pkgs;
       ]
     then
       libcIconv pkgs.libc
-    else if stdenv.hostPlatform.isDarwin then
-      darwin.libiconv
     else
       libiconvReal;