[test] Mark parallel-compile-tasks incompatible with future

This fixes failures on bots running with --extra-flags=--future

Change-Id: I9594f44db9cc749d02151b695300b5c888f2c99b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2617085
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71973}

tools/testrunner/local/variants.py

@@ -97,6 +97,7 @@ INCOMPATIBLE_FLAGS_PER_EXTRA_FLAG = {
   "--optimize-for-size": ["--max-semi-space-size=*"],
   "--stress_concurrent_allocation": ["--single-threaded-gc", "--predictable"],
   "--stress-flush-bytecode": ["--no-stress-flush-bytecode"],
+  "--future": ["--parallel-compile-tasks"],
   "--stress-incremental-marking": INCOMPATIBLE_FLAGS_PER_VARIANT["stress_incremental_marking"],
 }