dashboard: update Dragonfly tip policy for ABI change, add release builder

From golang/go#34958 (comment) :

> Go's DragonFly support policy is that we support the latest stable
> release primarily, but also try to keep DragonFly master passing, in
> prep for it to become the latest stable release.
>
> But that does mean we need one more builder at the moment.

Updates golang/go#34958
Updates golang/go#23060

Change-Id: I84be7c64eac593dee2252c397f9529deea13605a
Reviewed-on: https://go-review.googlesource.com/c/build/+/202478
Reviewed-by: Tobias Klauser <[email protected]>
Reviewed-by: Bryan C. Mills <[email protected]>

Author: bradfitz

dashboard/builders.go

@@ -331,6 +331,16 @@ var Hosts = map[string]*HostConfig{
 		env:         []string{"GOROOT_BOOTSTRAP=/usr/pkg/go112"},
 		OwnerGithub: "bsiegert",
 	},
+	// Our DragonFly builder doesn't yet run on GCE
+	// (golang.org/issue/23060), so @bradfitz currently runs the
+	// release version at home, and @tdfbsd runs one somewhere
+	// running the bleeding edge version.
+	"host-dragonfly-amd64-bradfitz": &HostConfig{
+		IsReverse:   true,
+		ExpectNum:   1,
+		env:         []string{"GOROOT_BOOTSTRAP=/usr/local/go"},
+		OwnerGithub: "bradfitz",
+	},
 	"host-dragonfly-amd64-tdfbsd": &HostConfig{
 		IsReverse:      true,
 		ExpectNum:      1,
@@ -2214,9 +2224,15 @@ func init() {
 				// (https://golang.org/issue/32836)
 				return false
 			}
-			return defaultBuildsRepoPolicy(repo, branch, goBranch)
+			return atLeastGo1(goBranch, 14) && defaultBuildsRepoPolicy(repo, branch, goBranch)
 		},
 	})
+	addBuilder(BuildConfig{
+		Name:              "dragonfly-amd64-5_6",
+		HostType:          "host-dragonfly-amd64-bradfitz",
+		shouldRunDistTest: noTestDir,
+		SkipSnapshot:      true,
+	})
 	addBuilder(BuildConfig{
 		Name:              "freebsd-arm-paulzhol",
 		HostType:          "host-freebsd-arm-paulzhol",

dashboard/builders_test.go

@@ -524,6 +524,14 @@ func TestBuilderConfig(t *testing.T) {
 		// that'll never be fixed.
 		{b("[email protected]", "net"), none},
 		{b("[email protected]", "net"), none},
+
+		{b("dragonfly-amd64", "go"), onlyPost},
+		{b("dragonfly-amd64", "net"), onlyPost},
+		{b("[email protected]", "net"), none}, // Dragonfly ABI changes only supported by Go 1.14+
+		{b("[email protected]", "go"), none},  // Dragonfly ABI changes only supported by Go 1.14+
+		{b("dragonfly-amd64-5_6", "go"), onlyPost},
+		{b("dragonfly-amd64-5_6", "net"), onlyPost},
+		{b("[email protected]", "net"), onlyPost},
 	}
 	for _, tt := range tests {
 		t.Run(tt.br.testName, func(t *testing.T) {