[infra] Create 32 bit clusterfuzz debug builder

No-Try: true
Bug: chromium:1196595
Change-Id: Id6fcb704cad66c5a41232821df30721e49ede2b6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2817613Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Liviu Rau <liviurau@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74002}

infra/mb/mb_config.pyl

@@ -139,6 +139,7 @@
       'V8 Clusterfuzz Linux64 ASAN - debug builder': 'debug_x64_asan',
       'V8 Clusterfuzz Linux64 ASAN arm64 - debug builder':
           'debug_simulate_arm64_asan',
+      'V8 Clusterfuzz Linux - debug builder': 'debug_x86',
       'V8 Clusterfuzz Linux ASAN arm - debug builder':
           'debug_simulate_arm_asan',
       'V8 Clusterfuzz Linux64 CFI - release builder':