[MacPorts] #54127: cppunit @1.14.0 should fallback to a MacPorts gcc if no system c++11 compliant compiler is being found

[MacPorts]

#54127: cppunit @1.14.0 should fallback to a MacPorts gcc if no system c++11
compliant compiler is being found
----------------------------------------+---------------------
 Reporter:  udbraumann                  |      Owner:
     Type:  defect                      |     Status:  new
 Priority:  Normal                      |  Milestone:
Component:  ports                       |    Version:
 Keywords:  c++11, powerpc, clang, gcc  |       Port:  cppunit
----------------------------------------+---------------------
 When upgrading cppunit to 1.14.0 I realized this trouble:
 {{{
 $ sudo port build cppunit
 --->  Computing dependencies for cppunitWarning: All compilers are either
 blacklisted or unavailable; defaulting to first fallback option
 Warning: All compilers are either blacklisted or unavailable; defaulting
 to first fallback option
 Warning: All compilers are either blacklisted or unavailable; defaulting
 to first fallback option
 Warning: All compilers are either blacklisted or unavailable; defaulting
 to first fallback option
 Warning: All compilers are either blacklisted or unavailable; defaulting
 to first fallback option
 Warning: All compilers are either blacklisted or unavailable; defaulting
 to first fallback option
 Warning: All compilers are either blacklisted or unavailable; defaulting
 to first fallback option

 Error: Cannot install clang-4.0 for the arch 'powerpc' because
 Error: its dependency libxml2 does not build for the required arch by
 default
 Error: and the configured universal_archs 'i386 ppc' are not sufficient.
 Error: Follow https://guide.macports.org/#project.tickets to report a bug.
 Error: Processing of port cppunit failed
 }}}

 I think it is not a good solution to set `clang-4.0` as fallback if the
 system (e.g. 10.5.8) has no XCode compiler supporting c++11, as long as
 MacPorts gcc (e.g. gcc-4.8 or newer) is sufficient for the c++11
 compliance. Once I called
 {{{
 sudo port upgrade cppunit configure.compiler=macports-gcc-4.8
 }}}
 I could smoothly build `cppunit`.

 BTW, with the present configuration `cppunit` is not even being downloaded
 if the search for a c++11 compliant compiler fails. For the problem
 description above I already had run the line with the workaround before.

--
Ticket URL: <https://trac.macports.org/ticket/54127>
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