Merge pull request #230919 from mikepurvis/nix-run-pyproject-build

python3Packages.build: specify mainProgram

pkgs/development/python-modules/build/default.nix

···
   ];
 
   meta = with lib; {
+    mainProgram = "pyproject-build";
     description = "Simple, correct PEP517 package builder";
     longDescription = ''
       build will invoke the PEP 517 hooks to build a distribution package. It