package/setools: needs wchar

Even though setools itself does not require wide chars, the configure
script needs them when testing for C99 support.

Since:
  - it is not clear whether wchar are mandatory for C99 or not,
  - only uClibc may miss support for wide chars,
  - using SELinux would probably involve rather big systems (i.e. glibc
    would not be such a huge overhead),
just make setools depend on the toolchain having widechar.

Fixes:
    http://autobuild.buildroot.org/results/051/051a7f72ebadd56407700c22b57e942f08eb1c09/
    http://autobuild.buildroot.org/results/a4b/a4b2a6f1920430af43c23239de17200e70951b3b/


    ...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Cc: Clayton Shotwell <clayton.shotwell@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>