Just got this from MATLAB support. It works. Guillame was close!
Please perform the following steps to generate and use a "Prototype" file and a "thunk" file in order to load the DLL without using a compiler.
1) On the computer with the compiler, execute the following command in the MATLAB Command Window to create the "Prototype" file and the "thunk" file. This step assumes that the DLL you wish to load is called "somedllfile.dll" and that the corresponding header file is called "someheaderfile.h".
>>loadlibrary('somedllfile.dll', 'someheaderfile.h', 'mfilename', 'someprototypefile');
2) Transfer both the generated "Prototype" file ("someprototypefile.m") and the generated "thunk" file ("somedllfile_thunk_pcwin64.dll") to the computer without the compiler. It is important to include the "thunk" file in this transfer, in addition to the "Prototype" file.
3) On the computer without the compiler, execute the following command in the MATLAB Command Window to load the DLL.
>>loadlibrary(‘somedllfile.dll’,@someprototypefile)
In this step, it is important to use the '@' symbol before the name of the "Prototype" file and to remove any quotes around the name of "Prototype" file.
After completing these steps, the library should be successfully loaded.