musl: glob-util: filter out . and .. even if GLOB_ALTDIRFUNC is not supported

musl neither support GLOB_ALTDIRFUNC nor GLOB_BRACE.
Let's make safe_glob() work even when GLOB_ALTDIRFUNC is not supported.
Currently, GLOB_BRACE is simply ignored when it is not supported.

src/include/musl/glob.h

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include_next <glob.h>
+
+#ifndef GLOB_ALTDIRFUNC
+#define GLOB_ALTDIRFUNC (1 << 9)
+#define gl_flags    __dummy1
+#define gl_closedir __dummy2[0]
+#define gl_readdir  __dummy2[1]
+#define gl_opendir  __dummy2[2]
+#define gl_lstat    __dummy2[3]
+#define gl_stat     __dummy2[4]
+#endif
+
+#ifndef GLOB_BRACE
+#define GLOB_BRACE      (1 << 10)
+#endif