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

fusl/src/crypt/crypt.c

+#include <unistd.h>
+#include <crypt.h>
+
+char *__crypt_r(const char *, const char *, struct crypt_data *);
+
+char *crypt(const char *key, const char *salt)
+{
+        /* This buffer is sufficiently large for all
+         * currently-supported hash types. It needs to be updated if
+         * longer hashes are added. The cast to struct crypt_data * is
+         * purely to meet the public API requirements of the crypt_r
+         * function; the implementation of crypt_r uses the object
+         * purely as a char buffer. */
+        static char buf[128];
+        return __crypt_r(key, salt, (struct crypt_data *)buf);
+}