build: add Wdate-time to Werror flags
build: add Wdate-time to Werror flags

-Wdate-time

    Warn when macros __TIME__, __DATE__ or __TIMESTAMP__ are encountered as
    they might prevent bit-wise-identical reproducible compilations.

This is supported by GCC and Clang.
https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
https://clang.llvm.org/docs/DiagnosticsReference.html#wdate-time

Former-commit-id: ce4ce8d14c9ee97d868c2aadbbb36163fd9d7dd9
syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin