Re: Have one GPR file build another with external variables

[Simon Wright <simon@pushface.org>]

If you're only concerned wih runtimes, you could maybe look at
_installing_ the runtime in different locations depending on the
release/debug mode?

For Cortex GNAT RTS I use this style in build_runtime.gpr, to install
either with the compiler (not that I ever do!) or in
~/cortex-gnat-rts/local/stm32f4 (for example). All the source files in
the runtime source end up in the one adainclude/ directory.

   package Install is
      case Common.Local is
         when "no" =>
            for Prefix use "arm-eabi/lib/gnat/";
         when "yes" =>
            for Prefix use project'Project_Dir & "../local/";
      end case;
      for Prefix use Install'Prefix & "stm32f4";
      for Sources_Subdir use "adainclude";
      for Ali_Subdir use "adalib";
      for Lib_Subdir use "adalib";
      for Required_Artifacts (".") use ("runtime.xml");
      for Required_Artifacts ("adalib") use ("adalib/stm32f407-flash.ld");
      for Install_Project use "false";
   end Install;

Common.Local is set by the scenario variable INSTALL_LOCALLY, but you
could equally use your BUILD variable, so that the RTS would end up in
/some/path/debug or /some/path/release, and your project would pick up
its runtime from whichever. Wouldn't even have to use the same build
variable in project and RTS, so long as the projject knows where to
look.