stdenvAdapters: set default_both_libraries for meson in makeStaticLibrary

The default value of `default_both_libraries` is 'shared'. This change
supplements the existing `default_library` flag for static builds.

pkgs/stdenv/adapters.nix

@@ -130,7 +130,10 @@ rec {
           "--disable-shared"
         ];
         cmakeFlags = (args.cmakeFlags or []) ++ [ "-DBUILD_SHARED_LIBS:BOOL=OFF" ];
-        mesonFlags = (args.mesonFlags or []) ++ [ "-Ddefault_library=static" ];
+        mesonFlags = (args.mesonFlags or []) ++ [
+          "-Ddefault_library=static"
+          "-Ddefault_both_libraries=static"
+        ];
       });
     });