Platform specific flags and universal variants

[Adam Mercer]

Hi

I recently modified the fftw-3 and fftw-3-single ports to use the
muniversal PortGroup, which greatly simplfies building a universal
port but am running into a annoying issue. FFTW needs to be compiled
so that it runs as fast as possible, I therefore need to pass specific
options to configure depending on the platform. Using the muniversal
PortGroup I achieve this with the following:

array set merger_configure_args {
    ppc    "--enable-fma"
    ppc64  "--enable-fma"
    i386   "--enable-sse2"
    x86_64 "--enable-sse2"
}

for the fftw-3 port. However I also need to ensure these flags are
applied for the appropriate platform when the port is not built
universally. As the above only effects when the port is being built
universally. I need another way to apply these flags when built for a
single platform. Is there a way I can specify platform variants that
are ignored when the port is built universally?

Cheers

Adam