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

fusl/src/passwd/fgetgrent.c

Index: fusl/src/passwd/fgetgrent.c
diff --git a/fusl/src/passwd/fgetgrent.c b/fusl/src/passwd/fgetgrent.c
new file mode 100644
index 0000000000000000000000000000000000000000..7d045fd22be977aa47eaed0890c5ce8b39af9bcc
--- /dev/null
+++ b/fusl/src/passwd/fgetgrent.c
@@ -0,0 +1,12 @@
+#define _GNU_SOURCE
+#include "pwf.h"
+
+struct group *fgetgrent(FILE *f)
+{
+	static char *line, **mem;
+	static struct group gr;
+	struct group *res;
+	size_t size=0, nmem=0;
+	__getgrent_a(f, &gr, &line, &size, &mem, &nmem, &res);
+	return res;
+}