compile error at `drawing.c: uv__get_cpu_speed` when compiling for iOS

error:

compile with Xcode 12, from default baranch

iOS is not a supported or regularly tested platform so it's possible something broke after libuv/libuv@87f076515937345fda1a1dbc598f34e65e1b81c7. Please send a pull request if you figure out the cause.