[build] Temporarily make ubsan bot use no snapshot

Currently mksnapshot fails due to ubsan issues. With a nosnap build it
will be easier to track down failures initially as normal test
failures, since mksnapshot isn't called with the sanitizer
environment variables.

NOTRY=true
TBR=jgruber@chromium.org

Bug: v8:7860
Change-Id: I897a8d307d90f545c80a90e1e1a2a632ffae1c3e
Reviewed-on: https://chromium-review.googlesource.com/1116783Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54051}

infra/mb/mb_config.pyl

@@ -444,8 +444,10 @@
       'minimal_symbols'],
     'release_x64_tsan_minimal_symbols': [
       'release_bot', 'x64', 'tsan', 'minimal_symbols'],
+    # TODO(machenbach): Remove nosnap config when test failures are resolved.
+    # https://crbug.com/v8/7860
     'release_x64_ubsan': [
-      'release_bot', 'x64', 'ubsan'],
+      'release_bot', 'x64', 'ubsan', 'v8_snapshot_none'],
     'release_x64_ubsan_vptr': [
       'release_bot', 'x64', 'ubsan_vptr'],
     'release_x64_ubsan_vptr_recover_edge': [