Change behavior to optionally require Unikernel env variables (#95)

This PR adds an optional `require-ukc-vars` argument to
`shared/ensure-common-build-run-vars.sh` to only require Unikernel envs
when `require-ukc-vars` is present. This enables `./build-docker.sh` to
work without specifying `UKC_TOKEN` and `UKC_METRO`.

# Checklist

- [x] Related issue: #94 
- [x] Changes proposed: Adds an optional `require-ukc-vars`
- [ ] @mentions of the person or team responsible for reviewing proposed
changes.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Introduce optional `require-ukc-vars` to conditionally enforce
`UKC_TOKEN`/`UKC_METRO`, and update Chromium headful/headless build/run
scripts to use it.
> 
> - **Shared**:
> - `shared/ensure-common-build-run-vars.sh`: Add optional
`require-ukc-vars` argument to conditionally require
`UKC_TOKEN`/`UKC_METRO`; update usage/help text.
> - **Chromium Images**:
> - `images/chromium-headful/*` and `images/chromium-headless/*`: Update
`build-unikernel.sh` and `run-unikernel.sh` to source
`ensure-common-build-run-vars.sh` with `require-ukc-vars`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
5c19f78. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Pieter Ouwerkerk <[email protected]>
Co-authored-by: Pieter Ouwerkerk <[email protected]>

Author: 3 people

images/chromium-headful/build-unikernel.sh

@@ -3,7 +3,7 @@
 # Move to the script's directory so relative paths work regardless of the caller CWD
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
 cd "$SCRIPT_DIR"
-source "$SCRIPT_DIR/../../shared/ensure-common-build-run-vars.sh" chromium-headful
+source "$SCRIPT_DIR/../../shared/ensure-common-build-run-vars.sh" chromium-headful require-ukc-vars
 source "$SCRIPT_DIR/../../shared/erofs-utils.sh"
 
 # Ensure the mkfs.erofs tool is available

images/chromium-headful/run-unikernel.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 # Move to the script's directory so relative paths work regardless of the caller CWD
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
 cd "$SCRIPT_DIR"
-source ../../shared/ensure-common-build-run-vars.sh chromium-headful
+source ../../shared/ensure-common-build-run-vars.sh chromium-headful require-ukc-vars
 
 kraft cloud inst rm $NAME || true
 

images/chromium-headless/build-unikernel.sh

@@ -3,7 +3,7 @@
 # Move to the script's directory so relative paths work regardless of the caller CWD
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
 cd "$SCRIPT_DIR"
-source ../../shared/ensure-common-build-run-vars.sh chromium-headless
+source ../../shared/ensure-common-build-run-vars.sh chromium-headless require-ukc-vars
 source ../../shared/erofs-utils.sh
 
 # Ensure the mkfs.erofs tool is present

images/chromium-headless/run-unikernel.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 # Move to the script's directory so relative paths work regardless of the caller CWD
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
 cd "$SCRIPT_DIR"
-source ../../shared/ensure-common-build-run-vars.sh chromium-headless
+source ../../shared/ensure-common-build-run-vars.sh chromium-headless require-ukc-vars
 
 kraft cloud inst rm "$NAME" || true
 

shared/ensure-common-build-run-vars.sh

@@ -3,25 +3,33 @@ set -e -o pipefail
 
 IMAGE_TYPE=$1
 if [ -z "$IMAGE_TYPE" ]; then
-    echo "Usage: source ensure-common-build-run-vars.sh <image-type>"
+    echo "Usage: source ensure-common-build-run-vars.sh <image-type> [require-ukc-vars]"
     echo "e.g. source ensure-common-build-run-vars.sh chromium-headful"
+    echo "     source ensure-common-build-run-vars.sh chromium-headful require-ukc-vars"
     echo "This will set the defaults for the image name and test instance name"
     echo "You can override the defaults by setting the IMAGE and NAME variables"
+    echo "Pass 'require-ukc-vars' as second argument to require UKC_TOKEN/UKC_METRO"
     return 1
 fi
 IMAGE="${IMAGE:-onkernel/${IMAGE_TYPE}-test:latest}"
 NAME="${NAME:-${IMAGE_TYPE}-test}"
 
 UKC_INDEX="${UKC_INDEX:-index.unikraft.io}"
 
-# fail if UKC_TOKEN, UKC_METRO are not set
-errormsg=""
-for var in UKC_TOKEN UKC_METRO; do
-    if [ -z "${!var}" ]; then
-        errormsg+="$var "
+# Only require UKC_TOKEN and UKC_METRO when explicitly requested
+# Pass "require-ukc-vars" as second argument to enable this check
+REQUIRE_UKC_VARS="${2:-}"
+
+if [ "$REQUIRE_UKC_VARS" == "require-ukc-vars" ]; then
+    # fail if UKC_TOKEN, UKC_METRO are not set
+    errormsg=""
+    for var in UKC_TOKEN UKC_METRO; do
+        if [ -z "${!var}" ]; then
+            errormsg+="$var "
+        fi
+    done
+    if [ -n "$errormsg" ]; then
+        echo "Required variables not set: $errormsg"
+        return 1
     fi
-done
-if [ -n "$errormsg" ]; then
-    echo "Required variables not set: $errormsg"
-    exit 1
 fi