ocpasswd: attempt to use sha2crypt only in glibc

uclibc's crypt(3) is so dumb it will not error if
$5$ is specified as salt, but not supported.

src/ocpasswd.c

@@ -69,7 +69,11 @@ crypt_int(const char *fpasswd, const char *username, const char *groupname,
 		exit(1);
 	}
 
+#ifdef TRY_SHA2_CRYPT
 	strcpy(salt, "$5$");
+#else
+	strcpy(salt, "$1$");
+#endif
 	p = salt + 3;
 
 	for (i = 0; i < sizeof(_salt); i++) {