Script was failing when called on libraries that do not import symbols, because
bash pipefail option was specified, and grep was used in some pipelines to
filter symbols, and grep returns status 1 when it doesn't match any lines. This
could cause the script to fail on some systems and configurations, such as the
clang-tidy CI configuration
https://cirrus-ci.com/task/4801670352207872?logs=ci#L6191 where the
libbitcoin_crypto_x86_shani.a library does not import symbols.
Fix check-deps.sh to check for weak symbols so it can detect when an exported
template function is used from another library.
In a previous version of this commit, this change caused an invalid dependency
in the consensus library on the TryParseHex template function from the util
library to be detected, and a suppression was added here. But #30377 removed
the invalid dependency so the suppression is no longer needed.
The invalid dependency and problem detecting weak symbol usage was originally
reported by Hennadii Stepanov in
https://github.com/bitcoin/bitcoin/pull/29015#issuecomment-2209258843
