Only use textureScale on macOS

This is darwin specific and some linux systems were triggering
it by mistake.

May fix fyne-io#1103

internal/driver/glfw/window.go

@@ -495,7 +495,7 @@ func (w *window) resized(_ *glfw.Window, width, height int) {
 }
 
 func (w *window) frameSized(viewport *glfw.Window, width, height int) {
-	if width == 0 || height == 0 {
+	if width == 0 || height == 0 || runtime.GOOS != "darwin" {
 		return
 	}