buildFHSEnv: allow specifying executableName explicitly

doc/build-helpers/special/fhs-environments.section.md

@@ -6,11 +6,13 @@ It uses Linux' namespaces feature to create temporary lightweight environments w
 Accepted arguments are:
 
 - `name`
-        The name of the environment, and the wrapper executable if `pname` is unset.
+        The name of the environment.
 - `pname`
-        The pname of the environment and the wrapper executable.
+        The pname of the environment.
 - `version`
         The version of the environment.
+- `executableName`
+        The name of the wrapper executable. Defaults to `pname` if set, or `name` otherwise.
 - `targetPkgs`
         Packages to be installed for the main host's architecture (i.e. x86_64 on x86_64 installations). Along with libraries binaries are also installed.
 - `multiPkgs`

pkgs/build-support/build-fhsenv-bubblewrap/default.nix

@@ -15,6 +15,7 @@
   runScript ? "bash",
   nativeBuildInputs ? [ ],
   extraInstallCommands ? "",
+  executableName ? args.pname or args.name,
   meta ? { },
   passthru ? { },
   extraPreBwrapCmds ? "",
@@ -49,7 +50,6 @@ let
   inherit (pkgsHostTarget) pkgsi686Linux;
 
   name = args.name or "${args.pname}-${args.version}";
-  executableName = args.pname or args.name;
   # we don't know which have been supplied, and want to avoid defaulting missing attrs to null. Passed into runCommandLocal
   nameAttrs = lib.filterAttrs (
     key: value: