plv8: unbreak build, bump to version 2.3.8

ee58a5b30d broke the plv8 build because it
upgraded the v8_6_x expression everywhere to the 6.9 branch, which came
with API changes. Notably, it seems plv8 only supports up-to v8 6.4.x at
this time.

This keeps a copy of the plv8_6_x expression inside the same directory
as the other v8 versions (so patches, etc are easy to apply), but it is
not exposed to the top-level of all-packages.nix.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

pkgs/servers/sql/postgresql/plv8/default.nix

@@ -2,7 +2,7 @@
 
 stdenv.mkDerivation rec {
   name = "plv8-${version}";
-  version = "2.1.0";
+  version = "2.3.8";
 
   nativeBuildInputs = [ perl ];
   buildInputs = [ v8 postgresql ];
@@ -11,16 +11,20 @@ stdenv.mkDerivation rec {
     owner = "plv8";
     repo = "plv8";
     rev = "v${version}";
-    sha256 = "1sfpxz0zcbinn6822j12lkwgrw9kfacrs83ic968rm489rl9w241";
+    sha256 = "0hrmn1zzzdf52zwldg6axv57p0f3b279l9s8lbpijcv60fqrzx16";
   };
 
+  makeFlags = [ "--makefile=Makefile.shared" ];
+
   preConfigure = ''
-    substituteInPlace Makefile --replace '-lv8_libplatform' '-lv8_libplatform -lv8_libbase'
+    patchShebangs ./generate_upgrade.sh
   '';
 
+  buildPhase = "make -f Makefile.shared all";
+
   installPhase = ''
     mkdir -p $out/bin
-    install -D plv8.so                                         -t $out/lib
+    install -D plv8*.so                                        -t $out/lib
     install -D {plls,plcoffee,plv8}{--${version}.sql,.control} -t $out/share/extension
   '';