Random libraries in Linux

I'd been having some issues with the Linux box not compiling things like

emerge -1 =dev-perl/libintl-perl-1.240.0-r2

It would stop and saying

skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/../../../../lib64/libiconv.so when searching for -liconv

I searched for ages and found there was indeed a libincov but you can't have that installed at the same time as new glibc.

Hmm... OK what package installed these things.  Looks like gcc 5.3.0.  Recompile that.. nope... try older gcc.. nope.

Newb mistake there. The number of .. parent links takes it right out of the gcc folders. Right pack to /usr/lib/

Ok what package installed it? Equery, the package manager query tool

equery b libiconv.so.2.5.0

returned nothing. Meaning no package installed it. Tried taking off the .so versions numbers etc still the same.

What the?  OK this is crazy how about just deleting it.  If anything needs it it will re-install it surely.

All of a sudden

emerge -1 =dev-perl/libintl-perl-1.240.0-r2

worked again. The texinfo etc ones with the same errors worked.

So having extra unwanted libraries is as dangerous as not having the right libraries.  More so, because you think they're OK.  I guess at some stage I've installed somethign that has left them there or a Gentoo package has changed and not cleaned up after itself nicely.

Either way , weird problem.