> It should print a message about being installed on an unsupported
> system. Not having a Mac machine to test on, or having any clue about
> where things should live means I can't write the installer portion of
> the build system.

Yes, it does say something like
Sorry, don't know how to install on your platform.
five or six lines before the end of the output (but I didn't see it at
first).

If you run scons as scons -s then you won't get those extra lines. They're a scons thing and unfortunately the script has no control over them.

Installation on a Mac should be pretty much the same as on Linux, or any
other unix-like platform. e.g. /usr/local/bin and /usr/local/include,
or elsewhere if there was a --prefix= option.

I've enabled this for the Mac too. Hope it doesn't break anything! Just run 'scons install' to install into /usr/local or add prefix=path to install somewhere else.

By the way, there is no "scons install" target listed in the help message.

I've now added this.

> (4) There seems to be no way to tell scons to use specific build options
>
> This has always been supported, but only just documented :-) Yhc picks
> up the CCFLAGS environment variable. Simply build as:
> CCFLAGS="-mcpu=g5" scons

Right. Unfortunately, scons does not seem to respect the CCFLAGS
variable when it is doing its own configuration tests. So on my
machine, scons cannot recognise the installed libgmp, because the test
for it requires certain C flags (-m64) to succeed, but these are not
passed through.