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

fusl/src/passwd/putspent.c

Index: fusl/src/passwd/putspent.c
diff --git a/fusl/src/passwd/putspent.c b/fusl/src/passwd/putspent.c
new file mode 100644
index 0000000000000000000000000000000000000000..55c41bbc300d4d7250e657404a8354e277b55f3c
--- /dev/null
+++ b/fusl/src/passwd/putspent.c
@@ -0,0 +1,13 @@
+#include <shadow.h>
+#include <stdio.h>
+
+#define NUM(n) ((n) == -1 ? 0 : -1), ((n) == -1 ? 0 : (n))
+#define STR(s) ((s) ? (s) : "")
+
+int putspent(const struct spwd *sp, FILE *f)
+{
+	return fprintf(f, "%s:%s:%.*ld:%.*ld:%.*ld:%.*ld:%.*ld:%.*ld:%.*lu\n",
+		STR(sp->sp_namp), STR(sp->sp_pwdp), NUM(sp->sp_lstchg),
+		NUM(sp->sp_min), NUM(sp->sp_max), NUM(sp->sp_warn),
+		NUM(sp->sp_inact), NUM(sp->sp_expire), NUM(sp->sp_flag)) < 0 ? -1 : 0;
+}