build: fix -Wformat-security check when compiling with GCC
build: fix -Wformat-security check when compiling with GCC

Debian GCC ignores -Wformat-security, without -Wformat, which
means when we test for it, it currently fails:

```bash
checking whether C++ compiler accepts -Wformat-security... no
...
configure:15907: checking whether C++ compiler accepts -Wformat-security
configure:15926: g++ -std=c++11 -c -g -O2 -Werror -Wformat-security  conftest.cpp >&5
cc1plus: error: '-Wformat-security' ignored without '-Wformat' [-Werror=format-security]
cc1plus: all warnings being treated as errors
```

Fix this by just combining the -Wformat and -Wformat-security checks
together.


Former-commit-id: b3f9c04c0e4334c1ba26f43c56666d8d894e046d
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin