The GenerateMain step needs to return the generated filename to the MSBuild targets, and it does so by writing out MSBuild xml which is then loaded into the MSBuild logic.
This also requires adding support for the ErrorHandler machinery, which the
MachO.cs file needs.
I considered extracting the Abi enum from the MachO.cs file, but it's used in
several places (including externally, such as binding-tools-for-swift), which
means this would be a rather disruptive change.
I also considered modifying MachO.cs to make it possible to build without the
ErrorHandler machinery, but since we'll need it all anyway eventually, I
decided against this option as well.
Add support for passing configuration from the MSBuild targets to our linker
steps using the linker's --custom-data option.
There are just two values being passed now, but this will grow significantly
over time as linker steps are implemented.
Rolf Bjarne Kvinge