Blocks are also symbols, so when we have a block,
we have to look for blocks instead of symbols.

Change-Id: I683e646c2c63754a0b27b299dfdbc1d87017fb99
Reviewed-on: https://swiftshader-review.googlesource.com/4542Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>