Refactor Gambit support

Refactor the build rule:
- Put files in $out/gambit instead of $out.
- Make the optimization setting easy to override.
- Make use of gccStdenv more explicit at this level.
- Support new-style runtime options for forcing UTF-8 I/O.
- Override the PACKAGE_VERSION and PACKAGE_STRING with git version.
- Note that the license is lgpl21, not lpgl2 (Note: also dual asl20).
- Try and fail to meaningfully add missing runtimeDeps.
- Build using NIX_BUILD_CORES.

pkgs/development/compilers/gambit/bootstrap.nix

@@ -1,6 +1,10 @@
-{ stdenv, fetchurl, autoconf, gcc, coreutils, ... }:
+# This derivation is a reduced-functionality variant of Gambit stable,
+# used to compile the full version of Gambit stable *and* unstable.
 
-stdenv.mkDerivation {
+{ gccStdenv, lib, fetchurl, autoconf, gcc, coreutils, gambit-support, ... }:
+# As explained in build.nix, GCC compiles Gambit 10x faster than Clang, for code 3x better
+
+gccStdenv.mkDerivation {
   pname = "gambit-bootstrap";
   version = "4.9.3";
 
@@ -16,29 +20,25 @@ stdenv.mkDerivation {
            CPP=${gcc}/bin/cpp CXXCPP=${gcc}/bin/cpp LD=${gcc}/bin/ld \
            XMKMF=${coreutils}/bin/false
     unset CFLAGS LDFLAGS LIBS CPPFLAGS CXXFLAGS
-    ./configure --prefix=$out
+    ./configure --prefix=$out/gambit
   '';
 
   buildPhase = ''
     # Copy the (configured) sources now, not later, so we don't have to filter out
     # all the intermediate build products.
-    mkdir -p $out ; cp -rp . $out/
+    mkdir -p $out/gambit ; cp -rp . $out/gambit/
 
     # build the gsc-boot* compiler
-    make bootstrap
+    make -j$NIX_BUILD_CORES bootstrap
   '';
 
   installPhase = ''
-    cp -fa ./ $out/
+    cp -fa ./ $out/gambit/
   '';
 
   forceShare = [ "info" ];
 
-  meta = {
+  meta = gambit-support.meta // {
     description = "Optimizing Scheme to C compiler, bootstrap step";
-    homepage    = "http://gambitscheme.org";
-    license     = stdenv.lib.licenses.lgpl2;
-    platforms   = stdenv.lib.platforms.unix;
-    maintainers = with stdenv.lib.maintainers; [ thoughtpolice raskin fare ];
   };
 }