cpptoml: builds failing for 10.13 and earlier: cmake cannot find libcxx

[mascguy (Christopher Nielsen)]

Details:

CMake Error at CMakeLists.txt:30 (find_package):
  By not providing "FindLIBCXX.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "LIBCXX", but
  CMake did not find one.

  Could not find a package configuration file provided by "LIBCXX" with any
  of the following names:

    LIBCXXConfig.cmake
    libcxx-config.cmake

  Add the installation prefix of "LIBCXX" to CMAKE_PREFIX_PATH or set
  "LIBCXX_DIR" to a directory containing one of the above files.  If "LIBCXX"
  provides a separate development package or SDK, be sure it has been
  installed.

​https://ports.macports.org/port/cpptoml/builds/

[mascguy (Christopher Nielsen)]

It looks like this port is using the project's default behavior, which includes building examples. But those aren't provided by the port anyway, so that phase can be disabled.

Meanwhile, based on comparing our current published binaries, the port simply provides architecture-independent components:

$ port contents cpptoml
  /opt/local/include/cpptoml.h
  /opt/local/lib/cmake/cpptoml/cpptomlConfig.cmake
  /opt/local/lib/cmake/cpptoml/cpptomlConfigVersion.cmake
  /opt/local/lib/cmake/cpptoml/cpptomlTargets.cmake

Based on initial testing on 10.12, we can provide the following two flags to CMake, to completely eliminate the need for compilation (and libcxx):

-DENABLE_LIBCXX:BOOL=OFF \
-DCPPTOML_BUILD_EXAMPLES:BOOL=OFF

That also allows us to remove the dependency on Boost, and simplify the portfile.

[Christopher Nielsen <mascguy@…>]

In d414dd3965b6298353ff45c76d81d2d36b7d496a/macports-ports (master):

cpptoml: eliminate compilation; declare noarch
Fixes: #65308