component/binutils: fix compilation on OBS

For slapos-node package compilation, we use DESTDIR pointing to temp
location and PREFIX pointing to future /opt/slapos.

Without this commit, bison look at wrong directory for data:

bison: cannot open file `/opt/slapos/parts/bison/share/bison/m4sugar/m4sugar.m4'

component/binutils/buildout.cfg

@@ -57,3 +57,4 @@ configure-options =
 environment =
   LDFLAGS=-L${gettext:location}/lib -lintl -Wl,-rpath=${gettext:location}/lib -Wl,-rpath=${zlib:location}/lib
   PATH=${texinfo7:location}/bin:${bison:location}/bin:${m4:location}/bin:%(PATH)s
+  BISON_PKGDATADIR=${bison:location}/share/bison