[MacPorts] #52699: cmake portgroup version 1.1

[MacPorts]

#52699: cmake portgroup version 1.1
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  Reporter:  mkae         |      Owner:  mkae
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  cmake        |
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Comment (by RJVB):

 Most of these changes have already been presented elsewhere (and for a
 large part, ratified as useful, just never incorporated). I can't find the
 tickets with a few quick searches, so here's a bit of background.

 First off, I've decided to give my variant a higher version, so both
 Michael's original and my more elaborate portgroup can co-exist (for the
 time being).

 changes include:
 - use `CMAKE_BUILD_TYPE=MacPorts`. Inspired by Debian's own build type,
 this allows us to specify all compiler settings via the well-known
 configure.* commands and exported via the environment. If one of CMake's
 predefined types is used the corresponding standard options will be
 *appended* to our options, which will override notably the optimisation
 options. Some parsing of configure.cppflags, configure.cflags and
 configure.cxxflags is done to ensure this works as expected, in lines
 145-200 .
 - add CMAKE_EXPORT_COMPILE_COMMANDS so that each compiler command is saved
 to an additional compile_commands.json file. Completely transparent for
 most purposes, but very useful if you want to open the source and existing
 build directory in KDevelop (which then won't rerun cmake with default
 settings).
 - `cmake.install_rpath` : a convenience function to construct
 `CMAKE_INSTALL_RPATH` in steps, working around the fact that cmake doesn't
 support incremental commandline variables.
 - lines 204-243 : ensure there's a compile_commands.json file, and
 generate a `.macports.${subport}.configure.cmd` file that summarises the
 configure details, as a more permanent reference than the information
 available through the logfile. There's been some discussion of adding this
 to "base", if that happens this feature will evidently disappear or be
 refactored.

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Ticket URL: <https://trac.macports.org/ticket/52699#comment:1>
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