Fixed utils build for musl (missing GLOB_ONLYDIR)

[rdbo]

The musl libc is missing GLOB_ONLYDIR on Alpine Linux. This PR manually defines GLOB_ONLYDIR to 0, which makes the utils compile and work again. Details:

$ apk info --who-owns /usr/include/glob.h 
/usr/include/glob.h is owned by musl-dev-1.2.4_git20230717-r2

$ cat /usr/include/glob.h | grep GLOB_
#ifndef _GLOB_H
#define _GLOB_H
#define GLOB_ERR      0x01
#define GLOB_MARK     0x02
#define GLOB_NOSORT   0x04
#define GLOB_DOOFFS   0x08
#define GLOB_NOCHECK  0x10
#define GLOB_APPEND   0x20
#define GLOB_NOESCAPE 0x40
#define GLOB_PERIOD   0x80
#define GLOB_TILDE       0x1000
#define GLOB_TILDE_CHECK 0x4000
#define GLOB_NOSPACE 1
#define GLOB_ABORTED 2
#define GLOB_NOMATCH 3
#define GLOB_NOSYS   4

After building and installing with this fix:

$ sudo v4l2loopback-ctl list
OUTPUT          CAPTURE         NAME
/dev/video2     /dev/video2     Dummy video device (0x0000)