After src snapshot 0c47b9c211e, the build began failing with:
In file included from ../../third_party/nasm/asm/assemble.c:178:
../../third_party/nasm/include/compiler.h:249:21: error: static
declaration of 'mempcpy' follows non-static declaration
249 | static inline void *mempcpy(void *dst, const void *src, size_t n)
| ^
/usr/include/string.h:71:8: note: previous declaration is here
71 | void *(mempcpy)(void * __restrict, const void * __restrict, size_t);
Fix the build by restoring a default definition of HAVE_MEMPCPY since
we have had mempcpy() since 13.1.