profiles: set EAPI 8

PMS says that PMs must assume EAPI 0 if it's not present, and not all PMs
support this (pkgcraft doesn't, for example, and Portage is looking to drop
it one day).

Just set EAPI 8. We do EAPI=5 in Gentoo right now for upgrade reasons but even
that isn't really necessary.

Signed-off-by: Sam James <sam@gentoo.org>

profiles/eapi

@@ -0,0 +1 @@
+8