[gitian] Don't call "make check-symbols"
[gitian] Don't call "make check-symbols"

Currently it does not recognise any of the C++11 symbols. We can re-enable this
when either we update it, or upstream migrates to C++11 and does so.

bitcoinsSG/zcash,bitcoinsSG/zcash,bitcoinsSG/zcash,bitcoinsSG/zcash,bitcoinsSG/zcash,bitcoinsSG/zcash