Error building on MacOS: "implicit declaration of function 'yaSSL_CleanUp' is invalid"

[rocketeerbkw]

The error is:

../deps/libmariadbclient/vio/vio.c:389:3: error: implicit declaration of function 'yaSSL_CleanUp' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  yaSSL_CleanUp();
  ^
1 error generated.
make: *** [Release/obj.target/vio/deps/libmariadbclient/vio/vio.o] Error 1

After a ton googling, I found there was a change in Xcode 12.x that breaks this for some reason. In Xcode 11.x this was emitted as a warning, not an error.

Since this library is abandoned, the solution is to downgrade to Xcode 11.x. You can find older versions at https://developer.apple.com/download/more/ (you have to have a developer account at apple).