gcc15, gccgo15, gfortran15, gnat15: init at 15.1.0

Changes: https://gcc.gnu.org/gcc-15/changes.html
Porting guide: https://gcc.gnu.org/gcc-15/porting_to.html

pkgs/by-name/gf/gfortran15/package.nix

@@ -0,0 +1,10 @@
+{ wrapCC, gcc15 }:
+wrapCC (
+  gcc15.cc.override {
+    name = "gfortran";
+    langFortran = true;
+    langCC = false;
+    langC = false;
+    profiledCompiler = false;
+  }
+)

pkgs/development/compilers/gcc/versions.nix

@@ -1,5 +1,6 @@
 let
   majorMinorToVersionMap = {
+    "15" = "15.1.0";
     "14" = "14.2.1.20250322";
     "13" = "13.3.0";
     "12" = "12.4.0";
@@ -16,6 +17,7 @@ let
     {
       # 3 digits: releases (14.2.0)
       # 4 digits: snapshots (14.2.1.20250322)
+      "15.1.0" = "sha256-4rCewhZg8B/s/7cV4BICZSFpQ/A40OSKmGhxPlTwbOo=";
       "14.2.1.20250322" = "sha256-I3ROhiU4jYaB2aci2Z3B/mvLLTjBBoCF1CL7uiHTmUM=";
       "13.3.0" = "sha256-CEXpYhyVQ6E/SE6UWEpJ/8ASmXDpkUYkI1/B0GGgwIM=";
       "12.4.0" = "sha256-cE9lJgTMvMsUvavzR4yVEciXiLEss7v/3tNzQZFqkXU=";

pkgs/top-level/all-packages.nix

@@ -5967,6 +5967,7 @@ with pkgs;
   gcc12Stdenv = overrideCC gccStdenv buildPackages.gcc12;
   gcc13Stdenv = overrideCC gccStdenv buildPackages.gcc13;
   gcc14Stdenv = overrideCC gccStdenv buildPackages.gcc14;
+  gcc15Stdenv = overrideCC gccStdenv buildPackages.gcc15;
 
   # This is not intended for use in nixpkgs but for providing a faster-running
   # compiler to nixpkgs users by building gcc with reproducibility-breaking
@@ -6071,9 +6072,10 @@ with pkgs;
     gcc12
     gcc13
     gcc14
+    gcc15
     ;
 
-  gcc_latest = gcc14;
+  gcc_latest = gcc15;
 
   libgccjit = gcc.cc.override {
     name = "libgccjit";
@@ -6199,6 +6201,34 @@ with pkgs;
     }
   );
 
+  gnat15 = wrapCC (
+    gcc15.cc.override {
+      name = "gnat";
+      langC = true;
+      langCC = false;
+      langAda = true;
+      profiledCompiler = false;
+      # As per upstream instructions building a cross compiler
+      # should be done with a (native) compiler of the same version.
+      # If we are cross-compiling GNAT, we may as well do the same.
+      gnat-bootstrap =
+        if stdenv.hostPlatform == stdenv.targetPlatform && stdenv.buildPlatform == stdenv.hostPlatform then
+          buildPackages.gnat-bootstrap14
+        else
+          buildPackages.gnat15;
+      stdenv =
+        if
+          stdenv.hostPlatform == stdenv.targetPlatform
+          && stdenv.buildPlatform == stdenv.hostPlatform
+          && stdenv.buildPlatform.isDarwin
+          && stdenv.buildPlatform.isx86_64
+        then
+          overrideCC stdenv gnat-bootstrap14
+        else
+          stdenv;
+    }
+  );
+
   gnat-bootstrap = gnat-bootstrap12;
   gnat-bootstrap11 = wrapCC (
     callPackage ../development/compilers/gnat-bootstrap { majorVersion = "11"; }
@@ -6231,6 +6261,7 @@ with pkgs;
   gnat12Packages = recurseIntoAttrs (callPackage ./ada-packages.nix { gnat = buildPackages.gnat12; });
   gnat13Packages = recurseIntoAttrs (callPackage ./ada-packages.nix { gnat = buildPackages.gnat13; });
   gnat14Packages = recurseIntoAttrs (callPackage ./ada-packages.nix { gnat = buildPackages.gnat14; });
+  gnat15Packages = recurseIntoAttrs (callPackage ./ada-packages.nix { gnat = buildPackages.gnat15; });
   gnatPackages = gnat13Packages;
 
   inherit (gnatPackages)
@@ -6298,6 +6329,21 @@ with pkgs;
     }
   );
 
+  gccgo15 = wrapCC (
+    gcc15.cc.override {
+      name = "gccgo";
+      langCC = true; # required for go.
+      langC = true;
+      langGo = true;
+      langJit = true;
+      profiledCompiler = false;
+    }
+    // {
+      # not supported on darwin: https://github.com/golang/go/issues/463
+      meta.broken = stdenv.hostPlatform.isDarwin;
+    }
+  );
+
   ghdl-mcode = callPackage ../by-name/gh/ghdl/package.nix { backend = "mcode"; };
 
   ghdl-gcc = callPackage ../by-name/gh/ghdl/package.nix { backend = "gcc"; };