Bug#877818: gcc-6 build depends on removed transitional package realpath

[Adrian Bunk]

Source: gcc-6
Version: 6.4.0-7
Severity: serious

gcc-6 build depends on the transitional package realpath,
removed in coreutils 8.28-1.

The realpath program is part of the
(essential) coreutils package since 8.23-1.