blahaj: enable mt by default and add static (#270608)

pkgs/tools/misc/blahaj/default.nix

@@ -1,6 +1,10 @@
 { lib
+, stdenv
 , crystal
 , fetchFromGitHub
+  # https://crystal-lang.org/2019/09/06/parallelism-in-crystal/
+, multithreading ? true
+, static ? stdenv.hostPlatform.isStatic
 }:
 
 crystal.buildCrystalPackage rec {
@@ -14,6 +18,8 @@ crystal.buildCrystalPackage rec {
     hash = "sha256-CmMF9jDKUo+c8dYc2UEHKdBDE4dgwExcRS5sSUsUJik=";
   };
 
+  buildTargets = [ "${if static then "static" else "build"}${if multithreading then "_mt" else ""}" ];
+
   meta = with lib; {
     description = "Gay sharks at your local terminal - lolcat-like CLI tool";
     homepage = "https://blahaj.queer.software";