[gentoo-user] Broken binary packages

[Alexander Puchmayr <alexander.puchmayr@linznet.at>]

Hi there,

I'm using a build host to generate all packages for my different machines in my 
local network; Not every machine gets every package. 

I encountered a problem where a package that looks absolutely fine on the 
buildhost but on the target machine its broken since some libraries are 
missing. NB: I previously did an emerge -e world before on the buildhost.

As an example I'd like to take media-tv/mythtv-31.0-r1, which has a dependency 
to dev-qt/qtwebkit:5 if the xmltv useflag is set:

buildhost-desktop ~ # equery depends dev-qt/qtwebkit-5.212.0_pre20200309-r1
 * These packages depend on dev-qt/qtwebkit-5.212.0_pre20200309-r1:
dev-python/PyQt5-5.14.2 (webkit ? dev-qt/qtwebkit:5[printsupport])
dev-qt/designer-5.14.2 (webkit ? >=dev-qt/qtwebkit-5.9.1:5)
dev-util/kdevelop-5.5.2 (webkit ? >=dev-qt/qtwebkit-5.212.0_pre20180120:5)
kde-apps/k3b-19.12.3 (webkit ? >=dev-qt/qtwebkit-5.212.0_pre20180120:5)
kde-apps/kdenlive-19.12.3-r3 (freesound ? >=dev-qt/
qtwebkit-5.212.0_pre20180120:5)
kde-apps/umbrello-19.12.3 (>=dev-qt/qtwebkit-5.212.0_pre20180120:5)
media-gfx/digikam-6.4.0-r1 (webkit ? >=dev-qt/qtwebkit-5.212.0_pre20180120:5)
media-gfx/wkhtmltopdf-0.12.5 (dev-qt/qtwebkit:5[printsupport])
media-tv/mythtv-31.0-r1 (xmltv ? dev-qt/qtwebkit:5)
net-misc/teamviewer-15.4.4445 (dev-qt/qtwebkit:5)

The Useflag "xmltv" is not set, but since the packages kde-apps/umbrello and  
media-gfx/wkhtmltopdf have a direct dependency to dev-qt/qtwebkit, it is 
installed on the buildhost. 
When building mythtv, it finds the webkit libraries and headers installed and 
uses it, even if the xmltv-useflag is NOT set(!), yielding a binary that has an 
implicit dependency to qtwebkit, but portage does not know of it.

When I install now the mythtv package on my laptop, where none of the other 
packages are installed that require qtwebkit, there's no need for portage to 
install it, and so we get a broken mythtv package. 

I see several ways to solve this, but none is really satisfying:
* set the xmltv use flag to mythtv to get an explict dependency -- I don't want 
it and I don't need it.
* rebuild mythtv on my 12-year old notebook locally -- nothing I'd really like 
to do.
* Install qtwebkit in the world set -- I don't like those library packages in 
the world set
* remove those packages requiring qtwebkit explicity, then rebuild mythtv, 
build package, install on notebook and rebuild/reinstall the removed packages 
on the buildhost again -- too cumbersome and I have the same problem again at 
the next update session. And mythtv is not the only package that may cause 
such problems, so I would have to do this in many different combinations.

Is there a better way to solve this? Is it possible to tell mythtv's build 
system to ignore the unwanted libraries if the xmltv use-flag is NOT set?

Regards
	Alex