gauche: remove dependency onto gaucheBootstrap

This reduces closure size of the built package by about a third.

The only reference to gaucheBootstrap in the built package was in
$out/share/gauche-0.98/0.9.13/package-templates/configure, where it is
incorrect: anyone using the template shipped with the gauche package
would have unintentially used the bootstrap version of gauche instead.

pkgs/development/interpreters/gauche/default.nix

@@ -21,6 +21,8 @@ stdenv.mkDerivation rec {
   '';
 
   postPatch = ''
+    substituteInPlace ext/package-templates/configure \
+      --replace "#!/usr/bin/env gosh" "#!$out/bin/gosh"
     patchShebangs .
   '';