Tweak build.zig to work with cross-compiling (#3225)

src/build.zig

@@ -59,6 +59,7 @@ pub fn addRaylib(b: *std.Build, target: std.zig.CrossTarget, optimize: std.built
                 raylib.linkSystemLibrary("dl");
                 raylib.linkSystemLibrary("m");
                 raylib.linkSystemLibrary("X11");
+                raylib.addLibraryPath(.{ .path = "/usr/lib" });
                 raylib.addIncludePath(.{ .path = "/usr/include" });
 
                 raylib.defineCMacro("PLATFORM_DESKTOP", null);