[MacPorts] #61201: root6: 10.8 build + portfile issues

[MacPorts]

#61201: root6: 10.8 build + portfile issues
--------------------------+--------------------------
 Reporter:  chrstphrchvz  |      Owner:  cjones051073
     Type:  defect        |     Status:  assigned
 Priority:  Normal        |  Milestone:
Component:  ports         |    Version:  2.6.3
 Keywords:                |       Port:  root6
--------------------------+--------------------------
 The 10.8 build has been failing. In some builds such as the
 [https://build.macports.org/builders/ports-10.8_x86_64-builder/builds/25804/steps
 /install-port/logs/stdio most recent one (2020-09-18 11:01:24)], C++14
 code (usage of `make_unique`) is trying to be compiled while using
 `-std=c++11`:
 {{{
 In file included from
 /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_science_root6/root6/work/root-6-22-02/core/base/v7/src/RError.cxx:17:
 /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_science_root6/root6/work/root-6-22-02/core/base/v7/inc/ROOT/RError.hxx:142:55:
 error: no member named 'make_unique' in namespace 'std'
    explicit RResultBase(RError &&error) :
 fError(std::make_unique<RError>(std::move(error))) {}
                                                  ~~~~~^
 /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_science_root6/root6/work/root-6-22-02/core/base/v7/inc/ROOT/RError.hxx:142:67:
 error: 'RError' does not refer to a value
    explicit RResultBase(RError &&error) :
 fError(std::make_unique<RError>(std::move(error))) {}
                                                                   ^
 /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_science_root6/root6/work/root-6-22-02/core/base/v7/inc/ROOT/RError.hxx:76:7:
 note: declared here
 class RError {
       ^
 2 errors generated.
 }}}

 There are possibly other minor issues in the portfile. Why not force using
 clang-mp-5.0 (which first gets added to `compiler.blacklist`) with
 `configure.compiler` rather than `compiler.fallback`? There is also how
 MacPorts' clang is normally be added as a runtime dependency for cling,
 however clang-mp-5.0 is not a version that will be used for this purpose.
 (It is potentially confusing to set the compiler after the compiler
 variables have already been read.)

-- 
Ticket URL: <https://trac.macports.org/ticket/61201>
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