[badsectoracula]

For #1: you already have multiple files in your source so nothing stops you from including the .c file if you feel like compiling a single c file from the command line without a build tool is needed (although when it comes to make usually you can have a single generic makefile that does the same job)

For #3: the #1 applies here too (although beware for static stuff conflicts) but in practice C code compiles fast enough for this to not be a problem

I can see #2 being an advantage, but TBH i think the case where you both need a custom malloc, assert, etc and not need a build tool where you can pass the configuration macros is kinda rare.