It should be string.h but strings.h in render/xhtml.c:21
cc1: warnings being treated as errors
render/xhtml.c: In function ‘ups_toc_renderer’:
render/xhtml.c:711: error: implicit declaration of function ‘memcpy’
render/xhtml.c:711: error: incompatible implicit declaration of built-in function ‘memcpy’
It should be string.h but strings.h in render/xhtml.c:21