In sci-visualization/mantid/mantid-2.3.2.ebuild:
> +sci-libs/gsl
> +dev-python/numpy
> +dev-cpp/muParser
> +opencascade? ( sci-libs/opencascade )
> +dev-python/sphinx
> +"
> +
> +DEPEND="${RDEPEND}
> +doc? ( app-doc/doxygen )
> +test? ( dev-util/cppcheck )"
> +
> +S="${WORKDIR}/${P}-Source"
> +BUILD_DIR="${WORKDIR}/${P}-Build"
> +
> +src_prepare() {
> +	epatch "${FILESDIR}/limits.patch" "${FILESDIR}/find-
opencascade.patch" "${FILESDIR}/gzip-of.patch"
You should never use bundled zlib. Please drop it and use zlib[minizip] 
instead. 
—Reply to this email directly or view it on GitHub[1].[2]
It's worse than that - the bundled zlib is itself part of a bundled 
sci-visualization/qtiplot !

Unfortunately there doesn't seem to be any option in CMake to use the 
system qtiplot or zlib. Interestingly it searches for system zlib and 
presumably uses it elsewhere in the build, but the build fails if the patch is 
not applied.

The build takes several hours on a fairly new machine and is 
temperamental to start with, so I don't feel capable of patching it to use 
system qtiplot or zlib.




--------
[1] https://github.com/gentoo-science/sci/pull/73/files#r4295203
[2] 
https://github.com/notifications/beacon/lfIVbCaEJ0Byp7tDeY3XsEfgdWNLs6N
gwFxopgt0bdvDSyS9d_RAPOBz82kF3XOB.gif