Add software backend to gpu build

Bug: skia:8548
Change-Id: If3853711f4b183f3b0437ae2b31525b0e6c88213
Reviewed-on: https://skia-review.googlesource.com/c/172120
Reviewed-by: Kevin Lubick <kjlubick@google.com>
diff --git a/experimental/canvaskit/canvaskit_bindings.cpp b/experimental/canvaskit/canvaskit_bindings.cpp
index a7fb875..4d9b73f 100644
--- a/experimental/canvaskit/canvaskit_bindings.cpp
+++ b/experimental/canvaskit/canvaskit_bindings.cpp
@@ -341,11 +341,11 @@
     function("currentContext", &emscripten_webgl_get_current_context);
     function("setCurrentContext", &emscripten_webgl_make_context_current);
     constant("gpu", true);
-#else
+#endif
     function("_getRasterN32PremulSurface", optional_override([](int width, int height)->sk_sp<SkSurface> {
         return SkSurface::MakeRasterN32Premul(width, height, nullptr);
     }), allow_raw_pointers());
-#endif
+
     function("getSkDataBytes", &getSkDataBytes, allow_raw_pointers());
     function("MakeSkCornerPathEffect", &SkCornerPathEffect::Make, allow_raw_pointers());
     function("MakeSkDiscretePathEffect", &SkDiscretePathEffect::Make, allow_raw_pointers());