Provide infrastructure to be able to build the uvc-gadget library as a
shared object and an executable which links against this as a dependency
to implment the reference 'uvc-gadget' application.

All existing cmake infrastructure is removed. This removes custom glob
support that was previously used by an early development for Android,
which is expected to be re-added later when required.

Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

The Android C library doesn't provide the glob() function which we use
in the configfs code. Add conditional compilation to cmake such that a
local copy of glob is automatically compiled if glob isn't provided.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

The glibc glob() implementation doesn't compile on Android due to
missing support for getlogin_r (before Android ABI 28) and to missing
__THROW, __THROWNL and __attribute_noinline__ macros.

getlogin_r is only used to implement support for the '~' path component
which we don't use in the uvc-gadget library, so we can compile it out.
The three macros can safely be defined as no-op.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

The glibc glob() implementation seems to be meant to be compilable
outside of glibc, but that clearly hasn't been tested for some time. Fix
compilation.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

The Android libc implementation (bionic) doesn't provide the glob()
function. To enable compilation of the UVC gadget library for Android,
import the glibc glob() implementation.

The glob.c and glob.h files are imported unmodified to ease copyright
management, even if they don't compile as-is. Compilation will be fixed
separately.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>