You need a clear vision for what you have written the first version of.
Covering the foreseeable needs of your own typical projects, with enough configurability to handle the variations you expect, is quite the opposite of offering general purpose abstractions and models like Make or CMake: not only designing for yourself vs. designing for the public, but prioritizing completeness (an opinionated solution to build your own projects with minimal manual effort) or generality (a tool that can be used for many different projects, ideally handling any C or C++ compilation job at the cost of specifying what to do explicitly).
In the first case, hardcoded GCC options are good enough until you need something more sophisticated; in the second case, hardcoded GCC options severely limit the potential users.
Covering the foreseeable needs of your own typical projects, with enough configurability to handle the variations you expect, is quite the opposite of offering general purpose abstractions and models like Make or CMake: not only designing for yourself vs. designing for the public, but prioritizing completeness (an opinionated solution to build your own projects with minimal manual effort) or generality (a tool that can be used for many different projects, ideally handling any C or C++ compilation job at the cost of specifying what to do explicitly).
In the first case, hardcoded GCC options are good enough until you need something more sophisticated; in the second case, hardcoded GCC options severely limit the potential users.