[MacPorts] #63460: cmake-3.21.2_0 fails to configure on older Xcode clang versions

[MacPorts]

#63460: cmake-3.21.2_0 fails to configure on older Xcode clang versions
---------------------+----------------------------
  Reporter:  tehcog  |      Owner:  michaelld
      Type:  defect  |     Status:  assigned
  Priority:  High    |  Milestone:
 Component:  ports   |    Version:  2.7.1
Resolution:          |   Keywords:  lion mavericks
      Port:  cmake   |
---------------------+----------------------------

Comment (by kencu):

 The error:
 {{{
 error: chosen constructor is explicit in copy-initialization
 }}}

 is discussed here <https://stackoverflow.com/questions/45029992/is-the-
 stdmap-default-constructor-explicit>

 I found a previous similar issue in another project that was fixed by
 supplying a specific constructor:

 https://github.com/USCiLab/cereal/issues/339

 So it appears we can possibly find a way to supply a specific constructor
 to fix the build with clang-3.4 and other older clang versions, or we can
 force clang-3.7 or newer, which appear to work.

-- 
Ticket URL: <https://trac.macports.org/ticket/63460#comment:19>
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