[MacPorts] #47595: mlt: add universal variant

[MacPorts]

#47595: mlt: add universal variant
--------------------------+-------------------
 Reporter:  ryandesign@…  |      Owner:  dan@…
     Type:  enhancement   |     Status:  new
 Priority:  Normal        |  Milestone:
Component:  ports         |    Version:
 Keywords:                |       Port:  mlt
--------------------------+-------------------
 A universal variant should be added to the mlt port. The reason given in
 the port for why it is disabled is:

 {{{
 # frei0r-plugins is not universal
 universal_variant   no
 }}}

 This is no longer correct; frei0r-plugins does have a universal variant
 now.

 Just removing these lines is not enough because mlt is not currently using
 `-arch` flags, which it should be doing anyway, even for non-universal
 builds.

 Just adding `-arch` flags to `CFLAGS` and `LDFLAGS` isn't enough either,
 because then the universal build fails, saying:

 {{{
 cannot use 'dependencies' output with multiple -arch options
 }}}

 To work around that we may need to use the muniversal portgroup.

-- 
Ticket URL: <https://trac.macports.org/ticket/47595>
MacPorts <https://www.macports.org/>
Ports system for OS X