build: add fietsje config and alias for Delve debugger

Test Plan: Debugged a running process using `bazel run :dlv`.

X-Origin-Diff: phab/D550
GitOrigin-RevId: 3bea727afc0cc275fac19238067d871c42beef19
diff --git a/build/fietsje/BUILD.bazel b/build/fietsje/BUILD.bazel
index 4a5d3fb..70b6639 100644
--- a/build/fietsje/BUILD.bazel
+++ b/build/fietsje/BUILD.bazel
@@ -6,6 +6,7 @@
         "dependency.go",
         "deps_cilium.go",
         "deps_containerd.go",
+        "deps_delve.go",
         "deps_gvisor.go",
         "deps_kubernetes.go",
         "deps_sqlboiler.go",
diff --git a/build/fietsje/deps_delve.go b/build/fietsje/deps_delve.go
new file mode 100644
index 0000000..747f3e2
--- /dev/null
+++ b/build/fietsje/deps_delve.go
@@ -0,0 +1,27 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+func depsDelve(p *planner) {
+	p.collect("github.com/go-delve/delve", "v1.4.1").use(
+		"github.com/google/go-dap",
+		"github.com/peterh/liner",
+		"github.com/cosiner/argv",
+		"golang.org/x/arch",
+		"go.starlark.net",
+	)
+}
diff --git a/build/fietsje/main.go b/build/fietsje/main.go
index 7aa020b..875d5f7 100644
--- a/build/fietsje/main.go
+++ b/build/fietsje/main.go
@@ -96,6 +96,9 @@
 	// used by deltagen
 	p.collectOverride("github.com/lyft/protoc-gen-star", "v0.4.14")
 
+	// for interactive debugging during development (//:dlv alias)
+	depsDelve(p)
+
 	// First generate the repositories starlark rule into memory. This is because rendering will lock all unlocked
 	// dependencies, which might take a while. If a use were to interrupt it now, they would end up with an incomplete
 	// repositories.bzl and would have to restore from git.