Right now src_test is defined to call emake -j1, to force serial make. On the other hand, parallel make usually speeds up building of the test-support binaries, and on modern autotools they also allow for parallel execution of tests.
PMS patch: http://git.overlays.gentoo.org/gitweb/?p=proj/pms.git;a=commit;h=3ec4b3c22582a8ec206bce1e93bab377d7b264b5 Portage patch: http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=9f14ed80e65a18da06e0834961ea032e3e830319
(In reply to comment #1) > PMS patch: > > http://git.overlays.gentoo.org/gitweb/?p=proj/pms.git;a=commit; > h=3ec4b3c22582a8ec206bce1e93bab377d7b264b5 Commit in master: http://git.overlays.gentoo.org/gitweb/?p=proj/pms.git;a=commit;h=70ec5eda6a11c196ceafefbf47dc80140fe29b8a