build2: move to pkgs/by-name, also move bootstrap to separate package

This triggers 1 "rebuild", however this is not really a rebuild.
This commit just moves `build2.passthru.bootstrap` to
`build2-bootstrap`, which is seen as a new package.
It is already build since it's a dependency of `build2`.

in conclusion this doesn't create any rebuilds

pkgs/by-name/bu/build2-bootstrap/package.nix

@@ -2,7 +2,6 @@
   lib,
   stdenv,
   fetchurl,
-  pkgs,
   buildPackages,
   fixDarwinDylibNames,
 }:
@@ -52,5 +51,28 @@ stdenv.mkDerivation rec {
       --subst-var-by isTargetDarwin '${toString stdenv.targetPlatform.isDarwin}'
   '';
 
-  inherit (pkgs.build2) passthru;
+  passthru = {
+    configSharedStatic =
+      enableShared: enableStatic:
+      if enableShared && enableStatic then
+        "both"
+      else if enableShared then
+        "shared"
+      else if enableStatic then
+        "static"
+      else
+        throw "neither shared nor static libraries requested";
+  };
+
+  meta = {
+    homepage = "https://www.build2.org/";
+    description = "Bootstrap for the 'build2' package, you most likely want to use that one";
+    license = lib.licenses.mit;
+    changelog = "https://git.build2.org/cgit/build2/tree/NEWS";
+    platforms = lib.platforms.all;
+    maintainers = with lib.maintainers; [
+      hiro98
+      r-burns
+    ];
+  };
 }

pkgs/by-name/bu/build2/package.nix

@@ -1,7 +1,8 @@
 {
   stdenv,
   lib,
-  build2,
+  # Break cycle by using self-contained toolchain for bootstrapping
+  build2-bootstrap,
   fetchurl,
   fixDarwinDylibNames,
   libbutl,
@@ -11,18 +12,9 @@
   enableStatic ? !enableShared,
 }:
 let
-  configSharedStatic =
-    enableShared: enableStatic:
-    if enableShared && enableStatic then
-      "both"
-    else if enableShared then
-      "shared"
-    else if enableStatic then
-      "static"
-    else
-      throw "neither shared nor static libraries requested";
+  inherit (build2-bootstrap.passthru) configSharedStatic;
 in
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (finalAttrs: {
   pname = "build2";
   version = "0.17.0";
 
@@ -33,26 +25,25 @@ stdenv.mkDerivation rec {
     "man"
   ];
 
-  setupHook = ./setup-hook.sh;
+  setupHook = build2-bootstrap.setupHook;
 
   src = fetchurl {
-    url = "https://pkg.cppget.org/1/alpha/build2/build2-${version}.tar.gz";
+    url = "https://pkg.cppget.org/1/alpha/build2/build2-${finalAttrs.version}.tar.gz";
     hash = "sha256-Kx5X/GV3GjFSbjo1mzteiHnnm4mr6+NAKIR/mEE+IdA=";
   };
 
   patches = [
     # Remove any build/host config entries which refer to nix store paths
     ./remove-config-store-paths.patch
-    # Pick up sysdirs from NIX_LDFLAGS
-    ./nix-ldflags-sysdirs.patch
-  ];
+  ]
+  ++ build2-bootstrap.patches;
 
   strictDeps = true;
   nativeBuildInputs = [
-    build2
+    build2-bootstrap
   ];
   disallowedReferences = [
-    build2
+    build2-bootstrap
     libbutl.dev
     libpkgconf.dev
   ];
@@ -94,14 +85,19 @@ stdenv.mkDerivation rec {
   '';
 
   passthru = {
-    bootstrap = build2;
+    bootstrap = build2-bootstrap;
     inherit configSharedStatic;
   };
 
   meta = {
-    homepage = "https://www.build2.org/";
+    inherit (build2-bootstrap.meta)
+      homepage
+      license
+      changelog
+      platforms
+      maintainers
+      ;
     description = "Build2 build system";
-    license = lib.licenses.mit;
     longDescription = ''
       build2 is an open source (MIT), cross-platform build toolchain
       that aims to approximate Rust Cargo's convenience for developing
@@ -114,12 +110,6 @@ stdenv.mkDerivation rec {
       at C/C++ projects as well as mixed-language projects involving
       one of these languages (see bash and rust modules, for example).
     '';
-    changelog = "https://git.build2.org/cgit/build2/tree/NEWS";
-    platforms = lib.platforms.all;
-    maintainers = with lib.maintainers; [
-      hiro98
-      r-burns
-    ];
     mainProgram = "b";
   };
-}
+})

pkgs/top-level/all-packages.nix

@@ -5934,11 +5934,6 @@ with pkgs;
 
   black-macchiato = with python3Packages; toPythonApplication black-macchiato;
 
-  build2 = callPackage ../development/tools/build-managers/build2 {
-    # Break cycle by using self-contained toolchain for bootstrapping
-    build2 = buildPackages.callPackage ../development/tools/build-managers/build2/bootstrap.nix { };
-  };
-
   # Dependency of build2, must also break cycle for this
   libbutl = callPackage ../development/libraries/libbutl {
     build2 = build2.bootstrap;