When using external libraries (with .lib files) and are getting linker errors like below, you are using an imcompatible import library (.lib) file.
Invalid OMF record type 0x21 (possibly COFF)
The reason for this is that your import library file was designed for MSVC. The one uses the COFF format, which is not compatible with Borland's OMF format.
To solve this, try the following and in preferred order: