How to cross-compile runit

[Charlie Brady <charlieb@e-smith.com>]

For those who might be interested, here's what's needed to be done to 
cross-compile runit. 

The Makefile as delivered assumes that it is possible to build binaries
and execute them in order to test for feature availability on the target.
You won't be able to do that in a cross compile environment. Instead, 
you'll need to do some hand testing to determine the correct answers to 
questions that make usually determines at build time.

# start with a clean slate
make clean

# Set up build tools
echo path/to/cc > conf-cc
echo path/to/cc -s > conf-ld

make compile load choose

# Detect and avoid imitation poll() libraries
# If trypoll builds and executes without error on the target
# set H to iopause.h2
H=iopause.h1
cp $H iopause.h

# Does target have 64bit long arithmetic?
# Test by building tryulong64 and executing on target
# set H to uint64.h2 if so
H=uint64.h1
cp $H uint64.h

# Does target have a short gid_t type?
# Test by building tryshsgr and executing on target
# set H to hasshsgr.h2 if so
make chkshsgr
H=hasshsgr.h1
cp $H hasshsgr.h

# All the configuration based on runtime results is now complete
# The rest are compile and/or link tests, and can be relied upon
make

--
Charlie