zig/doc/targets.md

# How to Add Support For More Targets

Create bootstrap code in std/bootstrap.zig and add conditional compilation
logic. This code is responsible for the real executable entry point, calling
main() and making the exit syscall when main returns.

How to pass a byvalue struct parameter in the C calling convention is
target-specific. Add logic for how to do function prototypes and function calls
for the target when an exported or external function has a byvalue struct.

Write the target-specific code in the standard library.

Update the C integer types to be the correct size for the target.

Make sure that `c_longdouble` codegens the correct floating point value.