Add a "fork" of musl as //fusl.

fusl/src/legacy/utmpx.c

Index: fusl/src/legacy/utmpx.c
diff --git a/fusl/src/legacy/utmpx.c b/fusl/src/legacy/utmpx.c
new file mode 100644
index 0000000000000000000000000000000000000000..c483e4ed1d65e2ed51b7dbdcd6d26617fc8cee68
--- /dev/null
+++ b/fusl/src/legacy/utmpx.c
@@ -0,0 +1,43 @@
+#include <utmpx.h>
+#include <stddef.h>
+#include "libc.h"
+
+void endutxent(void)
+{
+}
+
+void setutxent(void)
+{
+}
+
+struct utmpx *getutxent(void)
+{
+	return NULL;
+}
+
+struct utmpx *getutxid(const struct utmpx *ut)
+{
+	return NULL;
+}
+
+struct utmpx *getutxline(const struct utmpx *ut)
+{
+	return NULL;
+}
+
+struct utmpx *pututxline(const struct utmpx *ut)
+{
+	return NULL;
+}
+
+void updwtmpx(const char *f, const struct utmpx *u)
+{
+}
+
+weak_alias(endutxent, endutent);
+weak_alias(setutxent, setutent);
+weak_alias(getutxent, getutent);
+weak_alias(getutxid, getutid);
+weak_alias(getutxline, getutline);
+weak_alias(pututxline, pututline);
+weak_alias(updwtmpx, updwtmp);