AFAICS the only useful thing in tachyon is the binary, the library is pointless as it's static and no headers are installed at all. See http://blog.flameeyes.eu/2009/10/03/does-it-come-with-includes-or for the details.
+*tachyon-0.98.9-r1 (16 Apr 2010) + + 16 Apr 2010; Justin Lecher <jlec@gentoo.org> +files/0.98.9-ldflags.patch, + +tachyon-0.98.9-r1.ebuild: + Stop stripping by buildsystem, #314955; do not install static lib, + #315225; respect LDFLAGS +