groff: fix multilib install file conflicts

groff: fix multilib install file conflicts

Perl scripts ${bindir}/{gpinyin, groffer, grog} are ${libdir} related
and cause multilib install file conflicts:

| Error: Transaction check error:
|  file /usr/bin/gpinyin conflicts between attempted installs of groff-1.22.3-r0.core2_64 and lib32-groff-1.22.3-r0.x86
|  file /usr/bin/groffer conflicts between attempted installs of groff-1.22.3-r0.core2_64 and lib32-groff-1.22.3-r0.x86
|  file /usr/bin/grog conflicts between attempted installs of groff-1.22.3-r0.core2_64 and lib32-groff-1.22.3-r0.x86

Inherit multilib_script.bbclass to fix the errors.

(From OE-Core rev: df90cb1f4ee8918b0bc2a281b2d77444a0d037e7)

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>