apple_cgl.c: Fix error: call to undeclared function 'os_get_option'

Signed-off-by: Yurii Kolesnykov <root@yurikoles.com>
Fixes: 222b85328e ("mesa: replace most occurrences of getenv() with os_get_option()")
Reviewed-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Mel Henning <mhenning@darkrefraction.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38429>

src/glx/apple/apple_cgl.c

@@ -34,6 +34,7 @@
 
 #include "apple_cgl.h"
 #include "apple_glx.h"
+#include "util/os_misc.h"
 
 #ifndef OPENGL_FRAMEWORK_PATH
 #define OPENGL_FRAMEWORK_PATH "/System/Library/Frameworks/OpenGL.framework/Versions/A/OpenGL"