package/usbutils: select libiconv if needed

Since upstream commit 7c7fed30f7553b551fce3151fe315cf69e602065, which
first appeared in usbutils version 007, iconv is used when available.
Since then, the package has been failing to build when libiconv needs to
be provided by a library external to the C library. This commit fixes
that by selecting BR2_PACKAGE_LIBICONV when libiconv is not provided by
the toolchain.

Fixes:
 http://autobuild.buildroot.net/results/d7d/d7dedb754804242d020d1a0d34dd95c7c1074710//
 http://autobuild.buildroot.net/results/bca/bca14ce4fe05f087e1d8821670ba3165e9820a7f//
 http://autobuild.buildroot.net/results/665/665c064bf28a325a8bc4d9fe16f453be48472e57//
 http://autobuild.buildroot.net/results/b54/b543a3713949571b04dbd9c94f063fa0a186765b//
 http://autobuild.buildroot.net/results/6ea/6ea6cde91c2c6c49f56a08f37fef0c134eda40a0//

Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit 9fb56e0367022c2d18531fd2d9882dedfc68f31d)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/usbutils/Config.in

@@ -3,6 +3,7 @@ config BR2_PACKAGE_USBUTILS
 	depends on BR2_TOOLCHAIN_HAS_THREADS # libusb
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_9 # libusb
 	depends on BR2_PACKAGE_HAS_UDEV # needs hwdb
+	select BR2_PACKAGE_LIBICONV if !BR2_ENABLE_LOCALE
 	select BR2_PACKAGE_LIBUSB
 	help
 	  USB enumeration utilities

package/usbutils/usbutils.mk

@@ -11,6 +11,11 @@ USBUTILS_DEPENDENCIES = host-pkgconf libusb udev
 USBUTILS_LICENSE = GPL-2.0+ (utils) GPL-2.0 or GPL-3.0 (lsusb.py)
 USBUTILS_LICENSE_FILES = LICENSES/GPL-2.0-only.txt LICENSES/GPL-3.0-only.txt
 
+ifeq ($(BR2_PACKAGE_LIBICONV),y)
+USBUTILS_DEPENDENCIES += libiconv
+USBUTILS_LDFLAGS += -liconv
+endif
+
 # Nice lsusb.py script only if there's python 3.x
 ifeq ($(BR2_PACKAGE_PYTHON3),)
 define USBUTILS_REMOVE_PYTHON