New review comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/25204#discussion_r497950816

Comment:
1. https://github.com/gkv311/sview/blob/master/Makefile#L57 `make_build_args="FFMPEG_ROOT=${XBPS_CROSS_BASE}/usr/include` or just `/usr`, not sure.

2. patch https://github.com/gkv311/sview/blob/8be57493b851b8172dcab097fea19e18c46fcc37/include/StStrings/StStringStream.h#L23 to `__linux__`, perhaps? That header is weird.