Upgrade bc to 6.6.1 am: 306341a225 am: cdb14c26d9 am: 9e6368af49

Original change: https://android-review.googlesource.com/c/platform/external/bc/+/2768152

Change-Id: Iae388bc78f6759b2c75b600ee00e7e1a4e00ea4d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>