buddy: link with libm explicitly

pkgs/development/libraries/buddy/default.nix

···
   buildInputs = [ bison ];
   patches = [ ./gcc-4.3.3-fixes.patch ];
   configureFlags = [ "CFLAGS=-O3" "CXXFLAGS=-O3" ];
+  NIX_LDFLAGS = [
+    "-lm"
+  ];
   doCheck = true;
 
   meta = {