How to check for C preprocessor defines?

FYI, I found this post, but it discusses using build.zig: Check the presence of kernel macros in build.zig

I’m using a Makefile-based build system and passing defines via -cflags -D__print_serial --. I need to know if these Makefile-provided defines are accessible within @cImport(), or if there’s a different approach for Makefile-based builds.