trivial-builders: move into the directory named alike (#223429)

While searching for something different I wondered why there is a
trivial-builders.nix file next to the trivial-builders directory where
only tests live. Lets fix that.

pkgs/development/interpreters/lua-5/wrap-lua.nix

@@ -4,7 +4,7 @@
 , makeWrapper
 }:
 
-# defined in trivial-builders.nix
+# defined in trivial-builders
 # imported as wrapLua in lua-packages.nix and passed to build-lua-derivation to be used as buildInput
 makeSetupHook {
   name = "wrap-lua-hook";

pkgs/development/interpreters/octave/wrap-octave.nix

@@ -4,7 +4,7 @@
 , makeWrapper
 }:
 
-# Defined in trivial-builders.nix
+# Defined in trivial-builders
 # Imported as wrapOctave in octave/default.nix and passed to octave's buildEnv
 # as nativeBuildInput
 # Each of the substitutions is available in the wrap.sh script as @thingSubstituted@

pkgs/top-level/stage.nix

@@ -101,7 +101,7 @@ let
     };
 
   trivialBuilders = self: super:
-    import ../build-support/trivial-builders.nix {
+    import ../build-support/trivial-builders {
       inherit lib;
       inherit (self) runtimeShell stdenv stdenvNoCC haskell;
       inherit (self.pkgsBuildHost) shellcheck;