Add a static-only variant of snappy dependency

By using that in the hydra-node linking, we always link statically
against this library (could not easily have one derivation yield both,
.a and .so files)

flake.nix

@@ -41,7 +41,6 @@
           pkgs = import inputs.nixpkgs {
             inherit system;
             overlays = [
-              # FIXME: we are missing a static linked snappy (other libraries are provided through overlays)
               # This overlay contains libsodium and libblst libraries
               inputs.iohk-nix.overlays.crypto
               # This overlay contains pkg-config mappings via haskell.nix to use the

nix/hydra/project.nix

@@ -57,8 +57,13 @@ pkgs.haskell-nix.project {
         "-L${lib.getLib static-secp256k1}/lib"
         "-L${lib.getLib static-openssl}/lib"
         "-L${lib.getLib static-libblst}/lib"
+        "-L${lib.getLib static-snappy}/lib"
       ];
     })
+    # Always use static snappy (from overlay, see nix/static-libs.nix)
+    {
+      packages.hydra-node.ghcOptions = [ "-L${pkgs.lib.getLib pkgs.static-snappy}/lib" ];
+    }
     {
       # lib:ghc is a bit annoying in that it comes with it's own build-type:Custom, and then tries
       # to call out to all kinds of silly tools that GHC doesn't really provide.

nix/static-libs.nix

@@ -15,4 +15,8 @@ final: prev: {
   static-openssl = (final.openssl.override { static = true; });
   static-zlib = final.zlib.override { shared = false; };
   static-pcre = final.pcre.override { shared = false; };
+  # XXX: Not replicate the cmakeFlags but just drop the -DBUILD_SHARED_LIBS=ON from it
+  static-snappy = final.snappy.overrideDerivation (old: {
+    cmakeFlags = [ "-DSNAPPY_BUILD_TESTS=OFF" "-DSNAPPY_BUILD_BENCHMARKS=OFF" ];
+  });
 }