Detect SSE/SSE2 for libsquish.
Detect SSE/SSE2 for libsquish.

(cherry picked from commit b6259661cebd0e03fe4849425fbbdc7be03dcaf5)

pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1