Ensure bzlmod example tests are run (#2371)

A followup to
#2370 (comment)

.bazelci/presubmit.yml

@@ -630,13 +630,13 @@ tasks:
     name: bzlmod BCR presubmit
     platform: ubuntu2004
     working_directory: examples/bzlmod/hello_world
-    build_targets:
+    test_targets:
       - "//..."
   macos_bzlmod_bcr:
     name: bzlmod BCR presubmit
     platform: macos
     working_directory: examples/bzlmod/hello_world
-    build_targets:
+    test_targets:
       - "//..."
 
 buildifier:

examples/bzlmod/hello_world/BUILD.bazel

@@ -16,7 +16,7 @@ sh_test(
     name = "hello_world_test",
     srcs = ["hello_world_test.sh"],
     args = [
-        "$(rootpath :hello_world)",
+        "$(rlocationpath :hello_world)",
     ],
     data = [
         ":hello_world",

examples/bzlmod/hello_world/hello_world_test.sh

@@ -1,5 +1,19 @@
 #!/usr/bin/env bash
 
+# --- begin runfiles.bash initialization v3 ---
+# Copy-pasted from the Bazel Bash runfiles library v3.
+set -uo pipefail; set +e; f=bazel_tools/tools/bash/runfiles/runfiles.bash
+source "${RUNFILES_DIR:-/dev/null}/$f" 2>/dev/null || \
+  source "$(grep -sm1 "^$f " "${RUNFILES_MANIFEST_FILE:-/dev/null}" | cut -f2- -d' ')" 2>/dev/null || \
+  source "$0.runfiles/$f" 2>/dev/null || \
+  source "$(grep -sm1 "^$f " "$0.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/null || \
+  source "$(grep -sm1 "^$f " "$0.exe.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/null || \
+  { echo>&2 "ERROR: cannot find $f"; exit 1; }; f=; set -e
+# --- end runfiles.bash initialization v3 ---
+
+
+set -euo pipefail
+
 # MARK - Functions
 
 fail() {
@@ -12,10 +26,10 @@ fail() {
 if [[ "$#" -ne 1 ]]; then
   fail "Usage: $0 /path/to/hello_world"
 fi
-hello_world="$1"
+HELLO_WORLD="$(rlocation "$1")"
 
 # MARK - Test
 
-output="$( "${hello_world}" )"
-[[ "${output}" == "Hello, world!" ]] || \
-  fail 'Expected "Hello, world!", but was' "${output}"
+OUTPUT="$("${HELLO_WORLD}")"
+[[ "${OUTPUT}" == "Hello, world!" ]] ||
+  fail 'Expected "Hello, world!", but was' "${OUTPUT}"