Add initial support for building with extensions

src/sqlite.nix

@@ -13,9 +13,10 @@
   zlib,
   icu,
 
-  amalgamate,
-  features,
-  featureFlags,
+  amalgamate ? true,
+  coreInitExt ? null,
+  features ? { },
+  featureFlags ? [ ],
   enableInteractive ? false,
 
   ...
@@ -54,13 +55,15 @@ stdenv.mkDerivation (finalAttrs: {
     "--${if static then "disable" else "enable"}-shared"
     "--${if static then "enable" else "disable"}-static"
     "--${if amalgamate then "enable" else "disable"}-amalgamation"
+
   ] ++ lib.optional features.ENABLE_ICU [
     "--enable-icu-collations"
     "--with-icu-config=${lib.getExe' icu.dev "icu-config"}"
   ];
 
-  env.NIX_CFLAGS_COMPILE = lib.concatStringsSep " " featureFlags;
-  env.NIX_CFLAGS_LINK = lib.optionalString features.ENABLE_FTS5 "-lm";
+  makeTarget = if static then "lib" else "so";
+  makeFlags = (coreInitExt.passthru.makeFlags or [ ]) ++ map (opt: "OPTIONS+=${lib.escapeShellArg opt}") featureFlags;
 
-  makeTarget = "sqlite3.la";
+  env.NIX_CFLAGS_LINK = lib.optionalString features.ENABLE_FTS5 "-lm";
+  env.NIX_LDFLAGS = lib.concatStringsSep " " (coreInitExt.passthru.extraLDFLAGS or [ ]);
 })