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

fusl/src/passwd/putpwent.c

Index: fusl/src/passwd/putpwent.c
diff --git a/fusl/src/passwd/putpwent.c b/fusl/src/passwd/putpwent.c
new file mode 100644
index 0000000000000000000000000000000000000000..3a02e5730482044d56e1458b26360fefa3f85541
--- /dev/null
+++ b/fusl/src/passwd/putpwent.c
@@ -0,0 +1,10 @@
+#define _GNU_SOURCE
+#include <pwd.h>
+#include <stdio.h>
+
+int putpwent(const struct passwd *pw, FILE *f)
+{
+	return fprintf(f, "%s:%s:%d:%d:%s:%s:%s\n",
+		pw->pw_name, pw->pw_passwd, pw->pw_uid, pw->pw_gid,
+		pw->pw_gecos, pw->pw_dir, pw->pw_shell)<0 ? -1 : 0;
+}