From https://git.alpinelinux.org/aports/tree/community/procps-compat/musl-fixes.patch?id=781a465d3d41af56a6e4bf9d52b7273c87899e25

--- a/w.c
+++ b/w.c
@@ -55,11 +55,7 @@
 #include <termios.h>
 #include <time.h>
 #include <unistd.h>
-#ifdef HAVE_UTMPX_H
-#	include <utmpx.h>
-#else
-#	include <utmp.h>
-#endif
+#include <utmp.h>
 #include <arpa/inet.h>
 
 static int ignoreuser = 0;	/* for '-u' */
--- a/proc/escape.c
+++ b/proc/escape.c
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <string.h>
 #include <limits.h>
+#include <langinfo.h>
 #include "procps.h"
 #include "escape.h"
 #include "readproc.h"