use bionic bots instead of xenial for linux builder

We are retiring older distribution than bionic.

Bug: chromium:1199405
Change-Id: I9a2f7979ab4307a0948b0146f82a76186d7e0c6e
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/13481
Reviewed-by: Petr Hosek <phosek@google.com>
Commit-Queue: Takuto Ikuta <tikuta@google.com>

infra/config/generated/cr-buildbucket.cfg

diff --git a/infra/config/generated/cr-buildbucket.cfg b/infra/config/generated/cr-buildbucket.cfg
index 727d9a5..663243a 100644
--- a/infra/config/generated/cr-buildbucket.cfg
+++ b/infra/config/generated/cr-buildbucket.cfg
@@ -92,7 +92,7 @@
       name: "linux"
       swarming_host: "chromium-swarm.appspot.com"
       dimensions: "cpu:x86-64"
-      dimensions: "os:Ubuntu-16.04"
+      dimensions: "os:Ubuntu-18.04"
       dimensions: "pool:luci.flex.try"
       recipe {
         name: "gn"

infra/config/main.star

diff --git a/infra/config/main.star b/infra/config/main.star
index c896dfc..876d20b 100755
--- a/infra/config/main.star
+++ b/infra/config/main.star
@@ -151,6 +151,6 @@
         cq_group = "gn",
     )
 
-try_builder("linux", "Ubuntu-16.04")
+try_builder("linux", "Ubuntu-18.04")
 try_builder("mac", "Mac-10.15", caches = [swarming.cache("macos_sdk")])
 try_builder("win", "Windows-10", caches = [swarming.cache("windows_sdk")])