Make sure MYS2 is installed.  By default help desk install 64-bit.  Make sure help desk install 32-bit also.

So the package you need for 32-bit is:  mingw-w64-i686-toolchain

Launch the following command
C:\MSYS2\msys2_shell.cmd
 
Bruce.Tran@NGS-L-004085843 MSYS /c/tmp/htdp
$ export PATH=$PATH:/c/msys2/mingw32/bin
 
Bruce.Tran@NGS-L-004085843 MSYS /c/tmp/htdp
$ gfortran -DNGS_PC_ENV -static -m32 -Wall -Wtabs *.f -o htdp
 

After htdp.exe is created copy to htdp directory and commit back into svn.