[hwasan] Increase BB to explore for reachability

We pass mcpu=cortex-a55 for our build, which increases BB to the point
where the LLVM default of 32 is not enough. This caused worse coverage
for use-after-scope detection, and increased stack usage.

Test: build oriole_hwasan
Bug: 229654778
Change-Id: I6ddb47d7224a9c6ddbf2641c043e3430d330c5a9