Bug#962642: temporarily revert lib64 libraries

[Helmut Grohne]

Source: gmp
Version: 2:6.2.0+dfsg-5
Severity: important
User: helmutg at debian.org
Usertags: rebootstrap

gmp added a g++-multilib dependency. Doing so breaks cross building and
thus cross bootstrap. Please use a cross-translatable
g++-multilib-for-host dependency.  Unfortunately, gcc does not presently
provide those. They're being added in #666743. Therefore, I ask for
temporarily reverting the lib64 libraries and adding them once toolchain
dependency translation is supported by gcc.

Helmut