package/openvmtools: does not build with uClibc

On glibc 2.4+, openvmtools uses euidaccess(), which is not implemented
on uClibc.

But since uClibc fakes being a glibc-2.10, openvmtools believes it can
use euidaccess(), and thus we get a linking error.

Fixes:
    http://autobuild.buildroot.org/results/779/779bed269982f0b2e04baecae2e720d602319552/
    http://autobuild.buildroot.org/results/860/8609823e35115f07b0f16f0a1831201aa1cf9e3c/
    http://autobuild.buildroot.org/results/f57/f572573c5f7f9206e0a8309b535a7c633a2d6b16/


    ...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>