configure: check if pkg-config is installed

configure: check if pkg-config is installed

A few libraries need to be newer than a specific version in order to be
supported by fio and pkg-config utility is used to verify the versions
of the installed libraries. Since this step may fail because pkg-config
is not installed, verify pkg-config presence and warn the user if it
could not be found.

To avoid code duplication, add a common helper function to perform
these checks.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>