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

fusl/src/crypt/crypt_r.c

+#include <crypt.h>
+#include "libc.h"
+
+struct crypt_data;
+
+char *__crypt_des(const char *, const char *, char *);
+char *__crypt_md5(const char *, const char *, char *);
+char *__crypt_blowfish(const char *, const char *, char *);
+char *__crypt_sha256(const char *, const char *, char *);
+char *__crypt_sha512(const char *, const char *, char *);
+
+char *__crypt_r(const char *key, const char *salt, struct crypt_data *data)
+{
+        /* Per the crypt_r API, the caller has provided a pointer to
+         * struct crypt_data; however, this implementation does not
+         * use the structure to store any internal state, and treats
+         * it purely as a char buffer for storing the result. */
+        char *output = (char *)data;
+        if (salt[0] == '$' && salt[1] && salt[2]) {
+                if (salt[1] == '1' && salt[2] == '$')
+                        return __crypt_md5(key, salt, output);
+                if (salt[1] == '2' && salt[3] == '$')
+                        return __crypt_blowfish(key, salt, output);
+                if (salt[1] == '5' && salt[2] == '$')
+                        return __crypt_sha256(key, salt, output);
+                if (salt[1] == '6' && salt[2] == '$')
+                        return __crypt_sha512(key, salt, output);
+        }
+        return __crypt_des(key, salt, output);
+}
+
+weak_alias(__crypt_r, crypt_r);