The MSIL Assembler Action allows you to automate running of the ilasm.exe .IL assembler.

Source Files(s)
Type the pathnames of one or more .IL files to assemble (place each file on a new line.) Click the "Add file..." button to add a new source file.
Resource File (optional)
Optionally specify a .res file to include in the output file.
Output file (optional)
Optionally specify the output file path. If no path is specified, ilasm will output <sourcename>.exe or <sourcename>.dll, depending on the target type.
Create executable file (/exe) | Create DLL library file (/dll)
Specify whether to output an executable or a DLL file.
Sign with key (/key)
Specify whether to sign the compiled assembly with a key. Keys can be specified as key files (type the pathname to the key file) or as Key Sources (use the syntax @KeySourceName.)
Generate debug info (/debug)
If this option is selected, a .pdb file will be generated allowing you to debug the built assembly.
Suppress assembler progress output (/quiet)
Suppresses the progress details which are normally output by the assembler.
Directive Overrides
Each of these overrides corresponds to a directive which can be given in the .IL files. If an override value is specified here, it replaces the value(s) given in the source file(s).