stdenv/generic: introduce shellDryRun

Add `shellDryRun` to the generic stdenv and substitute it for uses of
`${stdenv.shell} -n`. The point of this layer of abstraction is to add
the flag `-O extglob`, which resolves #126344 in a more direct way.

nixos/modules/system/activation/top-level.nix

@@ -55,8 +55,8 @@ let
       substituteInPlace $out/dry-activate --subst-var out
       chmod u+x $out/activate $out/dry-activate
       unset activationScript dryActivationScript
-      ${pkgs.stdenv.shell} -n $out/activate
-      ${pkgs.stdenv.shell} -n $out/dry-activate
+      ${pkgs.stdenv.shellDryRun} $out/activate
+      ${pkgs.stdenv.shellDryRun} $out/dry-activate
 
       cp ${config.system.build.bootStage2} $out/init
       substituteInPlace $out/init --subst-var-by systemConfig $out

nixos/modules/system/boot/systemd.nix

@@ -210,20 +210,14 @@ let
   makeJobScript = name: text:
     let
       scriptName = replaceChars [ "\\" "@" ] [ "-" "_" ] (shellEscape name);
-      out = pkgs.writeTextFile {
+      out = (pkgs.writeShellScriptBin scriptName ''
+        set -e
+        ${text}
+      '').overrideAttrs (_: {
         # The derivation name is different from the script file name
         # to keep the script file name short to avoid cluttering logs.
         name = "unit-script-${scriptName}";
-        executable = true;
-        destination = "/bin/${scriptName}";
-        text = ''
-          #!${pkgs.runtimeShell} -e
-          ${text}
-        '';
-        checkPhase = ''
-          ${pkgs.stdenv.shell} -n "$out/bin/${scriptName}"
-        '';
-      };
+      });
     in "${out}/bin/${scriptName}";
 
   unitConfig = { config, options, ... }: {

pkgs/build-support/trivial-builders.nix

@@ -219,7 +219,7 @@ rec {
         ${text}
         '';
       checkPhase = ''
-        ${stdenv.shell} -n $out
+        ${stdenv.shellDryRun} $out
       '';
     };
 
@@ -246,7 +246,7 @@ rec {
         ${text}
         '';
       checkPhase = ''
-        ${stdenv.shell} -n $out/bin/${name}
+        ${stdenv.shellDryRun} $out/bin/${name}
       '';
     };
 
@@ -295,7 +295,7 @@ rec {
       checkPhase =
         if checkPhase == null then ''
           runHook preCheck
-          ${stdenv.shell} -n $out/bin/${name}
+          ${stdenv.shellDryRun} $out/bin/${name}
           ${shellcheck}/bin/shellcheck $out/bin/${name}
           runHook postCheck
         ''

pkgs/games/vdrift/default.nix

@@ -12,7 +12,7 @@
 , bullet
 , curl
 , gettext
-, writeTextFile
+, writeShellScriptBin
 
 , data ? fetchsvn {
     url = "svn://svn.code.sf.net/p/vdrift/code/vdrift-data";
@@ -54,21 +54,15 @@ let
     };
   };
   wrappedName = "vdrift-${version}-with-data-${toString data.rev}";
-in writeTextFile {
+in
+(writeShellScriptBin "vdrift"  ''
+  export VDRIFT_DATA_DIRECTORY="${data}"
+  exec ${bin}/bin/vdrift "$@"
+'').overrideAttrs (_: {
   name = wrappedName;
-  text = ''
-    export VDRIFT_DATA_DIRECTORY="${data}"
-    exec ${bin}/bin/vdrift "$@"
-  '';
-  destination = "/bin/vdrift";
-  executable = true;
-  checkPhase = ''
-    ${stdenv.shell} -n $out/bin/vdrift
-  '';
-} // {
   meta = bin.meta // {
     hydraPlatforms = [ ];
   };
   unwrapped = bin;
   inherit bin data;
-}
+})

pkgs/stdenv/generic/default.nix

@@ -112,7 +112,7 @@ let
       # are absolute unless we go out of our way to make them relative (like with CF)
       # TODO: This really wants to be in stdenv/darwin but we don't have hostPlatform
       # there (yet?) so it goes here until then.
-      preHook = preHook+ lib.optionalString buildPlatform.isDarwin ''
+      preHook = preHook + lib.optionalString buildPlatform.isDarwin ''
         export NIX_DONT_SET_RPATH_FOR_BUILD=1
       '' + lib.optionalString (hostPlatform.isDarwin || (hostPlatform.parsed.kernel.execFormat != lib.systems.parse.execFormats.elf && hostPlatform.parsed.kernel.execFormat != lib.systems.parse.execFormats.macho)) ''
         export NIX_DONT_SET_RPATH=1
@@ -168,6 +168,11 @@ let
       inherit overrides;
 
       inherit cc hasCC;
+
+      # Convenience for doing some very basic shell syntax checking by parsing a script
+      # without running any commands. Because this will also skip `shopt -s extglob`
+      # commands and extglob affects the Bash parser, we enable extglob always.
+      shellDryRun = "${stdenv.shell} -n -O extglob";
     }
 
     # Propagate any extra attributes.  For instance, we use this to