env/linux-x86-buster, dashboard: add netbase package to the host

This change adds the netbase package to the host. The netbase package
includes several components necessary for TCP/IP based networking.
Network related unit tests were failing on builders using this host
without this package.

Fixes golang/go#42750

Change-Id: Id98d46efac4fe98ecf475035218be181c3d8dec0
Reviewed-on: https://go-review.googlesource.com/c/build/+/272486
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/dashboard/builders.go b/dashboard/builders.go
index 8fce694..97035d5 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -1789,7 +1789,6 @@
 		env: []string{
 			"GO_DISABLE_OUTBOUND_NETWORK=1",
 		},
-		KnownIssue: 42750,
 	})
 	addBuilder(BuildConfig{
 		Name:     "linux-amd64-longtest",
diff --git a/env/linux-x86-buster/Dockerfile b/env/linux-x86-buster/Dockerfile
index 5744173..f6987ef 100644
--- a/env/linux-x86-buster/Dockerfile
+++ b/env/linux-x86-buster/Dockerfile
@@ -16,9 +16,11 @@
 # libc6-dev-i386 gcc-multilib: for 32-bit builds
 # procps lsof psmisc: misc basic tools
 # libgles2-mesa-dev libopenal-dev fonts-droid-fallback: required by x/mobile repo
+# netbase: for net package tests, issue 42750
 RUN apt-get update && apt-get install -y \
 	--no-install-recommends \
 	ca-certificates \
+	netbase \
 	curl \
 	gdb \
 	strace \