Reproduce the /proc error in chroot runners.

This works fine for regular runners that uses the docker image
user-space. But the next commit enables chroot runners and it starts to
fail.

bazel build \
    --remote_executor=grpc://localhost:8980 \
    --remote_instance_name=fuse \
    --remote_default_exec_properties OSFamily=linux \
    --remote_default_exec_properties container-image="docker://ghcr.io/catthehacker/ubuntu:act-22.04@sha256:5f9c35c25db1d51a8ddaae5c0ba8d3c163c5e9a4a6cc97acd409ac7eae239448" \
    @//:introspection

This is step one of three to verify the solution to:
buildbarn/bb-remote-execution#115

BUILD.bazel

@@ -1,8 +1,30 @@
+load("@aspect_bazel_lib//lib:run_binary.bzl", "run_binary")
 load("@bazel_gazelle//:def.bzl", "gazelle")
-load("@com_github_bazelbuild_buildtools//buildifier:def.bzl", "buildifier")
 
 # gazelle:prefix github.com/buildbarn/bb-deployments
 # gazelle:exclude dummy_for_dependencies.go
 gazelle(
     name = "gazelle",
 )
+
+# $ bazel build //cmd/ls-proc
+# $ cp -f bazel-bin/cmd/ls-proc/ls-proc_/ls-proc ls-proc
+run_binary(
+    name = "introspection",
+    outs = ["out"],
+    args = ["$(location out)"],
+    execution_requirements = {
+        "no-cache": "1",
+    },
+    tool = ":ls-proc",
+    srcs = [
+        # env is required in path resolution for chroot actions.
+        "usr/bin/env",
+        # Not strictly needed, but symmetric with sys and proc.
+        "dev/dummy",
+        # Send a directory for /sys and /proc
+        # Bazel wants a file for it to send the directory.
+        "sys/dummy",
+        "proc/dummy",
+    ],
+)

cmd/ls-proc/BUILD.bazel

@@ -0,0 +1,15 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["main.go"],
+    importpath = "github.com/buildbarn/bb-deployments/cmd/ls-proc",
+    visibility = ["//visibility:private"],
+)
+
+go_binary(
+    name = "ls-proc",
+    embed = [":go_default_library"],
+    visibility = ["//visibility:public"],
+    pure = "on",
+)

cmd/ls-proc/main.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"log"
+)
+
+func main() {
+	entries, err := os.ReadDir("/proc/self")
+	if err != nil {
+		log.Fatal("Reading /proc/self:", err)
+	}
+	if len(os.Args) == 1 {
+		log.Fatal("Usage: ls-proc <output file>")
+	}
+
+	max := 10
+	for i, e := range entries {
+		if i > max {
+			break
+		}
+		fmt.Println(e.Name())
+	}
+
+	os.Create(os.Args[1])
+}