Update crates_universe render script to run from Bazel (#2492)

crate_universe/DEVELOPMENT.md

@@ -38,5 +38,5 @@ A lot of crates are vendored into this repo, e.g. in examples and tests. To
 re-vendor them all, a bash script is provided:
 
 ```sh
-./util/vendor.sh
+bazel run //crate_universe/tools:vendor
 ```

crate_universe/tools/BUILD.bazel

@@ -5,3 +5,8 @@ filegroup(
     ],
     visibility = ["//crate_universe:__subpackages__"],
 )
+
+sh_binary(
+    name = "vendor",
+    srcs = ["vendor.sh"],
+)

crate_universe/tools/vendor.sh

@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 
+set -euo pipefail
+
 # A script to re-vendor all vendors crates in this repository.
 # This should be ran whenever any crate rendering changes.
 
@@ -15,7 +17,11 @@ vendor_workspace() {
     popd >/dev/null
 }
 
-workspaces="$(find -type f -name WORKSPACE.bazel -o -name WORKSPACE -o -name MODULE.bazel)"
+if [[ -n "${BUILD_WORKSPACE_DIRECTORY:-}" ]]; then
+    cd "${BUILD_WORKSPACE_DIRECTORY:-}"
+fi
+
+workspaces="$(find . -type f -name WORKSPACE.bazel -o -name MODULE.bazel)"
 
 for workspace in $workspaces
 do