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

fusl/src/passwd/fgetspent.c

Index: fusl/src/passwd/fgetspent.c
diff --git a/fusl/src/passwd/fgetspent.c b/fusl/src/passwd/fgetspent.c
new file mode 100644
index 0000000000000000000000000000000000000000..47473bdb8cd84c0f31f57a89c11e654747589852
--- /dev/null
+++ b/fusl/src/passwd/fgetspent.c
@@ -0,0 +1,15 @@
+#include "pwf.h"
+#include <pthread.h>
+
+struct spwd *fgetspent(FILE *f)
+{
+	static char *line;
+	static struct spwd sp;
+	size_t size = 0;
+	struct spwd *res = 0;
+	int cs;
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+	if (getline(&line, &size, f) >= 0 && __parsespent(line, &sp) >= 0) res = &sp;
+	pthread_setcancelstate(cs, 0);
+	return res;
+}