"Andrew Wilkinson"
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.
This should now work.
Actually, it still does not work. In the meantime, I worked out how to disable the config test for libgmp, which enabled me to discover in addition that although the CCFLAGS variable is given to the C compiler when building C files, it is not given to the C compiler when linking those object files together. Thanks for looking into all this! Regards, Malcolm