uae: fixup build

Fixes #62341. I'm not sure why the problem happened,
but the solution seems fairly simple and risk-free.

pkgs/misc/emulators/uae/default.nix

···
   buildInputs = [ gtk2 alsaLib SDL ];
 
   hardeningDisable = [ "format" ];
+  LDFLAGS = [ "-lm" ];
 
   meta = {
     description = "Ultimate/Unix/Unusable Amiga Emulator";