https://bugs.gentoo.org/880439#c10
--- a/getopt.c
+++ b/getopt.c
@@ -43,9 +43,9 @@
 #include <stdio.h>
 /* We're ANSI now; we're guaranteed to have strchr(). */
 #include <string.h>
+#include <unistd.h>
 
 #define ERR(s, c)	if(x_opterr){\
-	extern int write();\
 	char errbuf[2];\
 	errbuf[0] = c; errbuf[1] = '\n';\
 	(void) write(2, argv[0], (unsigned)strlen(argv[0]));\