build: auto-detect g++ -gz support
build: auto-detect g++ -gz support

Older combinations of g++/binutils don't support -gz, so auto-detect its
presence.

Fixes #3697.
Message-Id: <faeb68b810bcf0ebb02e1e72e05066f61e2363aa@scylladb.com>

avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla