* [ignition-plugin1] Add new port
* vcpkg_fixup_cmake_targets: Add DO_NOT_DELETE_PARENT_CONFIG_PATH
By default the vcpkg_fixup_cmake_targets script remove the parent
path of CONFIG_PATH if it named "cmake", this behaviour is not convenient
for ports that install more than one CMake package config file, and
for which vcpkg_fixup_cmake_targets is invoked multiple times.
To optionally disable this behaviour, this commit adds the option
DO_NOT_DELETE_PARENT_CONFIG_PATH to vcpkg_fixup_cmake_targets.
* [ignition-modularscripts] Add support for ignition libraries that install multiple CMake package config files
Some ignition libraries install several CMake package config files,
to represent the different components of the library. This commit modifies
the ignition_modular_library function to fixup correctly all the cmake package config files.
* vcpkg_fixup_pkgconfig: Move definition of SYSTEM_LIBRARIES to vcpkg_common_definitions
To correctly validate installed pkg-config files, vcpkg_fixup_pkgconfig needs to know
for each platform which libraries are not managed by vcpkg. This commits improve this
definitions for all the triplet supported by vcpkg, and move this definition to vcpkg_common_definitions
in a way that permit custom triplets to overload its value.
