So I came across the "-fsyntax-only" option supported by GCC/Clang/Mingw. With this flag set, the compiler will process the source code, output any warnings, errors, or diagnostic messages, but won't attempt to create any output files. It's a nice quick way to scan source code for errors, without the compiler littering your directories with object files.
It's also faster than a full compile too. And less disk access or churning if you still use an old mechanical monster.
As the open source compilers tend to be a little more strict about error checking than MSVC, that might be a good way to scan a project for errors, or deviations from standard C++, even if the project is Windows only.
I ran Mingw on some Outpost 2 level code, and it came back with some warnings about passing string literals to a char* parameter. Technically, string literals are read-only, so they should only be accepted by const char* parameters.