gpu: build virgl_render_server env in HashMap
gpu: build virgl_render_server env in HashMap

Follow up from crrev/c/3753417 to cleanup implementation.

BUG=b:237493180
TEST=env for virgl_render_server process still has radv_require_etc2=true

Change-Id: I9aa6f9d8eb92e78e8ab8053be5df6406d6411ea9
Signed-off-by: Ryan Neph <7a140012b58874b966883fce003938f5de9942f2@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3877549
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Commit-Queue: Yiwei Zhang <8740d9f1664e48d07df551c300bbdb1ae03f6b48@chromium.org>
Reviewed-by: Yiwei Zhang <8740d9f1664e48d07df551c300bbdb1ae03f6b48@chromium.org>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm