It seems with this chumped CL 

https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/884731

Moblab has stopped building

-2012.1-r4: namespace std { struct bidirectional_iterator_tag; struct random_access_iterator_tag; }
qhull-2012.1-r4:                        ^
qhull-2012.1-r4: 6 errors generated.
qhull-2012.1-r4: make[2]: *** [CMakeFiles/qhullcpp.dir/build.make:183: CMakeFiles/qhullcpp.dir/src/libqhullcpp/QhullFacetSet.cpp.o] Error 1
qhull-2012.1-r4: make[2]: Leaving directory '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/work/qhull-2012.1_build'
qhull-2012.1-r4: make[1]: *** [CMakeFiles/Makefile2:253: CMakeFiles/qhullcpp.dir/all] Error 2
qhull-2012.1-r4: make[1]: Leaving directory '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/work/qhull-2012.1_build'
qhull-2012.1-r4: make: *** [Makefile:128: all] Error 2
qhull-2012.1-r4:  * ERROR: media-libs/qhull-2012.1-r4::portage-stable failed (compile phase):
qhull-2012.1-r4:  *   emake failed
qhull-2012.1-r4:  * 
qhull-2012.1-r4:  * If you need support, post the output of `emerge --info '=media-libs/qhull-2012.1-r4::portage-stable'`,
qhull-2012.1-r4:  * the complete build log and the output of `emerge -pqv '=media-libs/qhull-2012.1-r4::portage-stable'`.
qhull-2012.1-r4:  * The complete build log is located at '/build/guado_moblab/tmp/portage/logs/media-libs:qhull-2012.1-r4:20180124-224630.log'.
qhull-2012.1-r4:  * For convenience, a symlink to the build log is located at '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/temp/build.log'.
qhull-2012.1-r4:  * The ebuild environment file is located at '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/temp/environment'.
qhull-2012.1-r4:  * Working directory: '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/work/qhull-2012.1_build'
qhull-2012.1-r4:  * S: '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/work/qhull-2012.1'
qhull-2012.1-r4: >>> Failed to emerge media-libs/qhull-2012.1-r4 for /build/guado_moblab/, Log file:
qhull-2012.1-r4: >>>  '/build/guado_moblab/tmp/portage/logs/media-libs:qhull-2012.1-r4:20180124-224630.log'
qhull-2012.1-r4: 
qhull-2012.1-r4:  * Messages for package media-libs/qhull-2012.1-r4 merged to /build/guado_moblab/:
qhull-2012.1-r4: 
qhull-2012.1-r4:  * ERROR: media-libs/qhull-2012.1-r4::portage-stable failed (compile phase):
qhull-2012.1-r4:  *   emake failed
qhull-2012.1-r4:  * 
qhull-2012.1-r4:  * If you need support, post the output of `emerge --info '=media-libs/qhull-2012.1-r4::portage-stable'`,
qhull-2012.1-r4:  * the complete build log and the output of `emerge -pqv '=media-libs/qhull-2012.1-r4::portage-stable'`.
qhull-2012.1-r4:  * The complete build log is located at '/build/guado_moblab/tmp/portage/logs/media-libs:qhull-2012.1-r4:20180124-224630.log'.
qhull-2012.1-r4:  * For convenience, a symlink to the build log is located at '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/temp/build.log'.
qhull-2012.1-r4:  * The ebuild environment file is located at '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/temp/environment'.
qhull-2012.1-r4:  * Working directory: '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/work/qhull-2012.1_build'
qhull-2012.1-r4:  * S: '/build/guado_moblab/tmp/portage/media-libs/qhull-2012.1-r4/work/qhull-2012.1'
=== Complete: job qhull-2012.1-r4 (0m6.6s) ===
Failed media-libs/qhull-2012.1-r4 (in 0m6.6s). Your build has failed.
Pending 11/733, [Time 14:46:37 | Elapsed 40m39.7s | Load 2.95 10.53 24.3]
Packages failed:
	media-libs/qhull-2012.1-r4