dashboard: update Debian version for 386 builders

This change updates various linux-386 builders after the release of
bullseye:
- linux-386 has been updated to bullseye.
- linux-386-jessie has had the notes updated.
- linux-386-buster has been added.

Updates golang/go#47721

Change-Id: Iab0048fcad4d51839013074a51ad37b424d3a7af
Reviewed-on: https://go-review.googlesource.com/c/build/+/343632
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 814fc41..c724e31 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -1524,9 +1524,10 @@
 	})
 	addBuilder(BuildConfig{
 		Name:           "linux-386",
-		HostType:       "host-linux-jessie",
+		HostType:       "host-linux-bullseye",
 		distTestAdjust: fasterTrybots,
 		tryBot:         defaultTrySet(),
+		Notes:          "Debian stable (currently Debian bullseye).",
 		env: []string{
 			"GOARCH=386",
 			"GOHOSTARCH=386",
@@ -1888,10 +1889,9 @@
 		},
 	})
 	addBuilder(BuildConfig{
-		Name:       "linux-386-jessie",
-		HostType:   "host-linux-jessie",
-		Notes:      "Debian Jessie, 32-bit builder. Same as the normal 'linux-386' builder at this time, but with -jessie suffix. Used for release builds.",
-		buildsRepo: disabledBuilder, // Disabled because the "linux-386" builder does identical work.
+		Name:     "linux-386-jessie",
+		HostType: "host-linux-jessie",
+		Notes:    "Debian Jessie, 32-bit builder.",
 		env: []string{
 			"GOARCH=386",
 			"GOHOSTARCH=386",
@@ -1909,6 +1909,16 @@
 		},
 	})
 	addBuilder(BuildConfig{
+		Name:     "linux-386-buster",
+		HostType: "host-linux-buster",
+		Notes:    "Debian Buster, 32-bit builder.",
+		env: []string{
+			"GOARCH=386",
+			"GOHOSTARCH=386",
+			"GO_DISABLE_OUTBOUND_NETWORK=1",
+		},
+	})
+	addBuilder(BuildConfig{
 		Name:     "linux-amd64-longtest",
 		HostType: "host-linux-stretch-morecpu",
 		Notes:    "Debian Stretch with go test -short=false",