stdenv adapter: Keep configureFlags a list

pkgs/stdenv/adapters.nix

@@ -34,9 +34,9 @@ rec {
   makeStaticBinaries = stdenv: stdenv //
     { mkDerivation = args: stdenv.mkDerivation (args // {
         NIX_CFLAGS_LINK = "-static";
-        configureFlags =
-          toString args.configureFlags or ""
-          + " --disable-shared"; # brrr...
+        configureFlags = (args.configureFlags or []) ++ [
+            "--disable-shared" # brrr...
+          ];
       });
       isStatic = true;
     };
@@ -47,9 +47,10 @@ rec {
   makeStaticLibraries = stdenv: stdenv //
     { mkDerivation = args: stdenv.mkDerivation (args // {
         dontDisableStatic = true;
-        configureFlags =
-          toString args.configureFlags or ""
-          + " --enable-static --disable-shared";
+        configureFlags = (args.configureFlags or []) ++ [
+          "--enable-static"
+          "--disable-shared"
+        ];
       });
     };