package/ltrace: Fix "unmet direct dependencies"

Fixes build error in elfutils
http://autobuild.buildroot.net/results/37f/37f87ad7ba087d42d0001f55305f7468c2a172b6/

eblwstrtab.c:(.text+0x43): undefined reference to `wmempcpy'
eblwstrtab.c:(.text+0x1ba): undefined reference to `wcslen'
eblwstrtab.c:(.text+0x2df): undefined reference to `wmemcmp'

because ltrace did not take into account that elfutils depends on
BR2_LARGEFILE & BR2_USE_WCHAR. This is also visible here:

wget http://autobuild.buildroot.net/results/37f/37f87ad7ba087d42d0001f55305f7468c2a172b6/defconfig


make defconfig BR2_DEFCONFIG=defconfig

warning: (BR2_PACKAGE_LTRACE) selects BR2_PACKAGE_ELFUTILS which has unmet direct
dependencies (BR2_LARGEFILE && BR2_USE_WCHAR && !BR2_avr32 && !BR2_bfin)

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>