Oleg Vinichenko

The dep can look like (probably):
RDEPEND="$(python_gen_cond_dep 'dev-python/configparse[${PYTHON_USEDEP}]' 'python2*')"

is your account update to use 2FA? Please, try with 
https://auth.funtoo.org/login

this is due to mesa update accident. Please, sync your meta-repo and you will get back to good version of media-libs/mesa

run 
epro build current

enabled in cinnamon for now.

no, this doesn`t require rebuild at all.
The very major version updastes, such 5 to 6 or 6 to 7 do require such rebuilds.

stage3 is a basic Funtoo linux image that is built from sources of software packages list, which is necessary minimal set of software which will allow your to run Funtoo linux on top of linux kernel. This list is carefully crafted and forms  a special set, called @system
to rebuild all of relevant packages from sources on your machine, use
emerge -e @system

rm -rf /var/tmp/portage

the fix to this will be applied soon.

yes, this is known bug. i reported it to usptream
https://bugs.gentoo.org/635678

su - or su -l is recommended as in this case you're getting clean environment not contaminated with any variables such as XDG_CACHE_HOME and which was the origin of a failure.

peak size used by temporary directory where debian-sources compiling is about 17GB. 20GB is set in ebuild with some exceeding margin to ensure it's enough space.

the problem is reported in https://bugs.funtoo.org/browse/FL-4576
the imagemagick-7 support patch is ready which will allow to remove the strict  dependency on older imagemagick and hence resolving the conflict.

the compilation stopped due to resource exhaustion, due to lack of RAM or having no swap.
 

the flora repo looks the one. It is a community contribution repository for cases like this.

i havent seen such behavior. But will look in a fresh test.

this is not intuitive to users, the time you can remove the uses can be the time those uses are no longer present in ebuilds or you don't need them. the first case can be determined when portage will give you a following message during emerge -auDN 
app-foo/bar (-use%), that means this use is no longer present (removed)
personally i trying to avoid using package.use too much and rely on what is enabled by default in profiles.

There are no specific LLVM_TARGETS for the Intel, take a look into brief News i made some time back, when llvm_targets introduced into Funtoo.
https://www.funtoo.org/News:LLVM_Targets

ah, i really stuck with xorg-server mask in my head. the xorg-server mask is fixed but xorg-drivers mask is something added after that and it's not overridden yet.

yes

no, this is no longer needed.

the build failure is not the same, now you need to rebuild dev-cpp/libcmis
did you by chance updated gcc? please, show output of gcc-config -l

the version for chromium specified in this thread can be compiled with the version of gcc in portage tree. that's 5.4.0

this is fixed 2 days ago

this will bring meta-repo up-to-date.