‘strcmp’ was not declared in this scope

strcmp function is declared in string.h try to put

#include <string.h> 

in DynamicLibrary.cpp and stderr is defained in stdio.h so put that too

#include <stdio.h>

From time to time I found open source code with missing header files as well.

UPDATE:

If you have different name, you can search include directory,

in real GNU/Linux bash (should work with Windows 10 WSL as well) you can use this to search for function:

find /usr/include -type f | xargs grep ' strcmp\s*\('

and this for variable:

find /usr/include -type f | xargs grep '[\s*]stdin\s*;'

on Git Bash on Windows there is /include and /mingw64/include directories but on my installation there were only ImageMagick header files and /mingw64/include/gnumake.h