update_engine: Remove unused binder_service_brillo.*

Chrome OS is not using this class. Just remove it.

Also cleanup the use cases of USE_OMAHA and USE_BINDER. USE_OMAHA is
only used in Chrome OS, and USE_BINDER is only used in Android, So it
doesn't make sense to have USE_OMAHA macros inside USE_BINDER.

BUG=chromium:977320
TEST=unittest

Change-Id: I4e302273585b7e105b177da01fe6dab07ad41676
Reviewed-on: https://chromium-review.googlesource.com/1669973
Tested-by: Amin Hassani <ahassani@chromium.org>
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 3e54eef..2ee0b9e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -69,7 +69,7 @@
     "__CHROMEOS__",
     "_FILE_OFFSET_BITS=64",
     "_POSIX_C_SOURCE=199309L",
-    "USE_BINDER=${use.binder}",
+    "USE_BINDER=0",
     "USE_DBUS=${use.dbus}",
     "USE_FEC=0",
     "USE_HWID_OVERRIDE=${use.hwid_override}",