Almost warning come from #warning, we can:
1.Add -Wno-cpp to disable #warning for precheck/nightly build:
https://stackoverflow.com/questions/9793293/how-do-i-disable-warning-message-in-gcc
2.Fix the remaining real warnning
3.Enable -Werror for precheck/nightly build
The suggestion from David is also valuable option for item 1, since
too much warning also block the developer find the real issue in daily
work. It is always good to enable people find the bug as early as
possible.
Sounds good to me.
