Can you please have a look if virtual/awk is sufficient or if gawk is needed.
awk is used for build and in the filters, but it looks all pretty posix.
+ 15 Feb 2013; Markos Chandras <hwoarang@gentoo.org> recoll-1.16.2.ebuild, + recoll-1.17.3-r1.ebuild, recoll-1.17.3.ebuild, recoll-1.18.1.ebuild: + Switch to virtual/awk. Bug #455646 +