Fix problems with GCC < v8
Fix problems with GCC < v8

Summary:
@public

GCC up until v7 flags our way of reading edges in `YGNodeSetStyleInputs` as unused variables. I managed to work around that by rearranging the casts a bit.

Reviewed By: SidharthGuglani

Differential Revision: D14299439

fbshipit-source-id: eec0266185504d1b790b9ef574bd4a83c0059d3a

facebook/yoga,facebook/yoga,facebook/yoga,facebook/yoga,facebook/css-layout,facebook/css-layout,facebook/css-layout,facebook/yoga,facebook/css-layout,facebook/css-layout,facebook/yoga,facebook/yoga,facebook/yoga,facebook/css-layout,facebook/css-layout,facebook/css-layout,facebook/yoga,facebook/css-layout,facebook/yoga