Add rpath for GN build of angle_end2end_tests.
Add rpath for GN build of angle_end2end_tests.

This fixes the static library build of this target on Linux.

BUG=angleproject:1270

Change-Id: Id65bd9b7136918829f385920b540a4df83650c6f
Reviewed-on: https://chromium-review.googlesource.com/320615
Tested-by: Kenneth Russell <1ebccd90c2bc76de65b6f830f2128a91ed69fdfb@chromium.org>
Tryjob-Request: Kenneth Russell <1ebccd90c2bc76de65b6f830f2128a91ed69fdfb@chromium.org>
Reviewed-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

MSOpenTech/angle,mlfarrell/angle,mlfarrell/angle,ecoal95/angle,mikolalysenko/angle,MSOpenTech/angle,ecoal95/angle,ecoal95/angle,ppy/angle,ppy/angle,ppy/angle,domokit/waterfall,mikolalysenko/angle,mlfarrell/angle,mikolalysenko/angle,ecoal95/angle,MSOpenTech/angle,MSOpenTech/angle,mlfarrell/angle,ecoal95/angle,domokit/waterfall,mikolalysenko/angle,ppy/angle