Getting Access to *FLAGS in build

[Michael Dickens]

I have a few ports which need access to various of the *FLAGS, as
created during the configure stage.  I've read through the code in
port1.0/portconfigure.tcl: configure_main, and it seems like it goes
through the process of creating the flags from those set mainly in
configure.*, pushed into the configure.env_array array.  Then, at the
end of portutil.tcl:command_exec, the array is deleted and thus is not
available for use in any other stage.  I can, of course, re-create the
actual *FLAGS, but that seems wasteful.  If I change 

environment_value_to_string