c++ .h.in file not found

I am working with the openssl library for c++. I used this library in another project and it would great. I carried it over to another project today and I'm having issues.

Two of the header files are .h.in files. (opensslv.h.in & configuration.h.in)

In the first project, this was not an issue. But in my new project it gives me an error on this line #include <openssl/configuration.h> because configuration.h cannot be found.

I get there is no literal configuration.h file but from what I understand that configuration.h.in file should generate a configuration.h file right?

Does anybody have any idea why that might be happening? Maybe I changed something in the project properties?