after #29396 removed `-L path/to/dir/of/libstdc++.so` from ld flags
See https://github.com/NixOS/nixpkgs/pull/29396#issuecomment-352600129
Module::Build build helper works correctly when LD is unset (taking LD from Perl
config to be `cc`). However, we can not unset LD because this goes contrary to
the cross compilation effort, and we can not make it propagate ld-is-cc-hook
because it breaks e.g. the build of `libguestfs`. However, #29396 makes LD=ld
incompatible with just 3 perl packages; they are individually fixed by this
commit.
69345ec37b