package/hidapi: select glibc gconv libs copy

package/hidapi: select glibc gconv libs copy

Hidapi source uses iconv_open UTF-16 conversion [1] which requires
gconv libararies when buiding with glibc in order to successfully
find serial number, manufacturer and product strings [2].

Use select in the config file to autmatically select gconv libararies
for inclusion on the target when building with glibc

Tested with ./utils/test-pkg -c hidapi.cfg -p hidapi and hidapi.cfg file
contents:
BR2_PACKAGE_HIDAPI=y
BR2_PACKAGE_EUDEV=y
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
BR2_USE_MMU=y
BR2_USE_WCHAR=y

Also tested on x86-64 build target with application using hidapi

[1]: https://github.com/signal11/hidapi/blob/a6a622ffb680c55da0de787ff93b80280498330f/libusb/hid.c#L446
[2]: https://www.silabs.com/community/interface/forum.topic.html/cp2114_linux_sta-RtWg

Signed-off-by: Dan Walkes <danwalkes@trellis-logic.com>
Tested-by: Dan Walkes <danwalkes@trellis-logic.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>