[ci] Reduce number of environment variables we send (#15730)

test/harness.ts

@@ -43,18 +43,27 @@ export const bunEnv: NodeJS.ProcessEnv = {
   BUN_FEATURE_FLAG_EXPERIMENTAL_BAKE: "1",
 };
 
+const ciEnv = { ...bunEnv };
+
 if (isWindows) {
   bunEnv.SHELLOPTS = "igncr"; // Ignore carriage return
 }
 
 for (let key in bunEnv) {
   if (bunEnv[key] === undefined) {
+    delete ciEnv[key];
     delete bunEnv[key];
   }
 
   if (key.startsWith("BUN_DEBUG_") && key !== "BUN_DEBUG_QUIET_LOGS") {
+    delete ciEnv[key];
     delete bunEnv[key];
   }
+
+  if (key.startsWith("BUILDKITE")) {
+    delete bunEnv[key];
+    delete process.env[key];
+  }
 }
 
 delete bunEnv.NODE_ENV;
@@ -1322,6 +1331,7 @@ export function getSecret(name: string): string | undefined {
     const { exitCode, stdout } = spawnSync({
       cmd: ["buildkite-agent", "secret", "get", name],
       stdout: "pipe",
+      env: ciEnv,
       stderr: "inherit",
     });
     if (exitCode === 0) {