The virtual is intended to be used for portable packages, along with portability.eclass' get_bmake function. So either: 1. fix your package to use get_bmake, if it can work with any form of BSD-like make, 2. fix your package to depend on sys-devel/pmake directly. However, note that sys-devel/pmake is dead and going to be lastrited soonish in favor of sys-devel/bmake.
I've changed the dep to unblock fixing virtual/pmake. Please decide whether you're happy with it as-is, or test it with bmake and if it works, update the ebuild to use get_bmake and the virtual. commit 6df2c95f45de3856dea091c058412b8be9fd93d2 Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Sat Jun 24 12:24:11 2017 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sat Jun 24 12:36:58 2017 net-analyzer/symon: Dep on sys-devel/pmake, #622598