buildShellEnv: Make prompt overridable

pkgs/build-support/dev-shell-tools/default.nix

···
     );
 
   buildShellEnv =
-    { drvAttrs }:
+    {
+      drvAttrs,
+      promptPrefix ? "build shell",
+      promptName ? null,
+    }:
     let
       name = drvAttrs.pname or drvAttrs.name or "shell";
       env = unstructuredDerivationInputEnv { inherit drvAttrs; };
···
         esac
 
         # Prefix a line to the prompt to indicate that we are in a build shell
-        PS1=$"\n(\[\033[1;33m\]build shell: \[\033[1;34m\]$name\[\033[1;33m\]\[\033[0m\]) $PS1"
+        PS1=$"\n(\[\033[1;33m\]"${lib.escapeShellArg promptPrefix}$": \[\033[1;34m\]"${
+          if promptName != null then lib.escapeShellArg promptName else ''"$name"''
+        }"\[\033[1;33m\]\[\033[0m\]) $PS1"
 
         runHook shellHook
       '';