Enable asserts on all builds.
Enable asserts on all builds.

The old build system never sets NDEBUG. This patch changes the cmake
build to have an equivalent behavior.

A regular release build now has compiler invocations with

 -DNDEBUG ... -UNDEBUG

If a project wants to disable asserts it can use Seastar_CXX_FLAGS. As
a test, configuring with

./configure.py --cflags=-DNDEBUG

produces compiler invocations with

-DNDEBUG ... -UNDEBUG ... -DNDEBUG

Signed-off-by: Rafael Ávila de Espíndola <1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>
Message-Id: <20181210171523.20747-1-1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>

syuu1228/seastar,syuu1228/seastar,syuu1228/seastar,cloudius-systems/seastar,scylladb/seastar,avikivity/seastar,avikivity/seastar,scylladb/seastar,dreamsxin/seastar,dreamsxin/seastar,cloudius-systems/seastar,scylladb/seastar,avikivity/seastar,dreamsxin/seastar,cloudius-systems/seastar