[MacPorts] #44397: qt5-mac: use conflicts_build portgroup

[MacPorts]

#44397: qt5-mac: use conflicts_build portgroup
--------------------------+------------------------
 Reporter:  ryandesign@…  |      Owner:  mcalhoun@…
     Type:  defect        |     Status:  new
 Priority:  Normal        |  Milestone:
Component:  ports         |    Version:  2.3.1
 Keywords:  haspatch      |       Port:  qt5-mac
--------------------------+------------------------
 qt5-mac doesn't build if qt4-mac is active.

 qt5-mac already has a prohibition on ''configuring'' while qt4-mac is
 active, but not on ''building''. To test whether qt5-mac can build while
 qt4-mac is active, I did the following:

 {{{
 sudo port -f deactivate qt4-mac
 sudo port configure qt5-mac
 sudo port activate qt4-mac
 sudo port build qt5-mac
 }}}

 The result was an immediate build failure per the attached main.log file.
 So qt5-mac should prohibit both configuring and building while qt4-mac is
 active. That's exactly what the conflicts_build portgroup is for, so I
 suggest using that, as in the attached patch.

-- 
Ticket URL: <https://trac.macports.org/ticket/44397>
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