fio: add optional dependency on libaio

fio can automatically detect and use libaio when available, so this
commit makes this optional dependency explicit.

Suggested by Charles <ckhardin@exablox.com> in bug #8851.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/fio/fio.mk

@@ -9,6 +9,10 @@ FIO_SITE = git://git.kernel.dk/fio.git
 FIO_LICENSE = GPLv2 + special obligations
 FIO_LICENSE_FILES = COPYING
 
+ifeq ($(BR2_PACKAGE_LIBAIO),y)
+FIO_DEPENDENCIES += libaio
+endif
+
 define FIO_CONFIGURE_CMDS
 	(cd $(@D); ./configure --cc="$(TARGET_CC)" --extra-cflags="$(TARGET_CFLAGS)")
 endef