LibGPU: Don't use relative paths for libsoftgpu in Lagom environments

We can count on the dynamic loader for each platform, and the RPATH of
our build infrastrucuture, to load the lib up automagically.

Userland/Libraries/LibGPU/Driver.cpp

@@ -18,9 +18,9 @@ static HashMap<String, String> const s_driver_path_map
 #if defined(__serenity__)
     { "softgpu", "libsoftgpu.so.serenity" },
 #elif defined(__APPLE__)
-    { "softgpu", "./liblagom-softgpu.dylib" },
+    { "softgpu", "liblagom-softgpu.dylib" },
 #else
-    { "softgpu", "./liblagom-softgpu.so" },
+    { "softgpu", "liblagom-softgpu.so.0" },
 #endif
 };