Refactor Gerbil support

- Use the new Gambit support.
- Move files from $out to $out/gerbil.
- Use new Gerbil configuration and installation scripts.
- Move some fixups from preBuild to postPatch.
- Give up on previous failed attempts at using static libraries.
- Add support for compiling libraries written in Gerbil.
- Build using NIX_BUILD_CORES.
- Register all those things in all-packages.

pkgs/development/compilers/gerbil/gerbil-support.nix

@@ -0,0 +1,63 @@
+{ pkgs, gccStdenv, callPackage, fetchFromGitHub }:
+# See ../gambit/build.nix regarding gccStdenv
+
+rec {
+  # Gerbil libraries
+  gerbilPackages-unstable = {
+  };
+
+  # Use this function in any package that uses Gerbil libraries, to define the GERBIL_LOADPATH.
+  gerbilLoadPath =
+    gerbilInputs : builtins.concatStringsSep ":" (map (x : x + "/gerbil/lib") gerbilInputs);
+
+  # Use this function to create a Gerbil library. See gerbil-utils as an example.
+  gerbilPackage = {
+    pname, version, src, meta, package,
+    git-version ? "", version-path ? "config/version.ss",
+    gerbil ? pkgs.gerbil-unstable,
+    gambit-params ? pkgs.gambit-support.stable-params,
+    gerbilInputs ? [],
+    buildInputs ? [],
+    softwareName ? "" } :
+    let buildInputs_ = buildInputs; in
+    gccStdenv.mkDerivation rec {
+      inherit src meta pname version;
+      buildInputs = [ gerbil ] ++ gerbilInputs ++ buildInputs_;
+      postPatch = ''
+        set -e ;
+        if [ -n "${version-path}" ] ; then
+          echo '(import :clan/utils/version)\n(register-software "${softwareName}" "${git-version}")\n' > "${version-path}"
+        fi
+        patchShebangs . ;
+      '';
+
+      postConfigure = ''
+        export GERBIL_BUILD_CORES=$NIX_BUILD_CORES
+        export GERBIL_PATH=$PWD/.build
+        export GERBIL_LOADPATH=${gerbilLoadPath gerbilInputs}
+        ${pkgs.gambit-support.export-gambopt gambit-params}
+      '';
+
+      buildPhase = ''
+        runHook preBuild
+        ./build.ss
+        runHook postBuild
+      '';
+
+      installPhase = ''
+        runHook preInstall
+        mkdir -p $out/gerbil/lib
+        cp -fa .build/lib $out/gerbil/
+        bins=(.build/bin/*)
+        if [ 0 -lt ''${#bins} ] ; then
+          cp -fa .build/bin $out/gerbil/
+          mkdir $out/bin
+          cd $out/bin
+          ln -s ../gerbil/bin/* .
+        fi
+        runHook postInstall
+      '';
+
+      dontFixup = true;
+    };
+}