dashboard: add openbsd/riscv64 builder

Updates golang/go#55999

Change-Id: I0e975e9010d40d68a8dbf57e1f90086e9b3b74dd
Reviewed-on: https://go-review.googlesource.com/c/build/+/515515
Reviewed-by: Aaron Bieber <deftly@gmail.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
diff --git a/dashboard/builders.go b/dashboard/builders.go
index f3536e1..94327ca 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -89,6 +89,7 @@
 	"openbsd-arm64":         "openbsd-arm64-jsing",
 	"openbsd-mips64":        "openbsd-mips64-jsing",
 	"openbsd-ppc64":         "openbsd-ppc64-n2vi",
+	"openbsd-riscv64":       "openbsd-riscv64-jsing",
 	"plan9":                 "plan9-arm",
 	"plan9-386":             "plan9-386-0intro",
 	"plan9-amd64":           "plan9-amd64-0intro",
@@ -525,6 +526,15 @@
 			"GOROOT_BOOTSTRAP=/home/gopher/go-openbsd-ppc64-bootstrap",
 		},
 	},
+	"host-openbsd-riscv64-joelsing": {
+		IsReverse:   true,
+		ExpectNum:   1,
+		Owners:      []*gophers.Person{gh("4a6f656c")},
+		GoBootstrap: "none",
+		env: []string{
+			"GOROOT_BOOTSTRAP=/home/gopher/go-openbsd-riscv64-bootstrap",
+		},
+	},
 	"host-plan9-386-0intro": {
 		IsReverse: true,
 		ExpectNum: 1,
@@ -2144,6 +2154,27 @@
 		tryBot:         nil,
 	})
 	addBuilder(BuildConfig{
+		Name:         "openbsd-riscv64-jsing",
+		HostType:     "host-openbsd-riscv64-joelsing",
+		KnownIssues:  []int{55999},
+		SkipSnapshot: true,
+		FlakyNet:     true,
+		buildsRepo: func(repo, branch, goBranch string) bool {
+			switch repo {
+			case "go", "net", "sys":
+				return branch == "master" && goBranch == "master"
+			default:
+				return false
+			}
+		},
+		distTestAdjust: noTestDirAndNoReboot,
+		tryBot:         nil,
+		env: []string{
+			// The machine is slow.
+			"GO_TEST_TIMEOUT_SCALE=3",
+		},
+	})
+	addBuilder(BuildConfig{
 		Name:           "netbsd-386-9_3",
 		HostType:       "host-netbsd-386-9_3",
 		distTestAdjust: noTestDirAndNoReboot,