Add the first Conan-based dependecies

add_conan_lib cmake function is defined, that allows to add a dependency using Conan with two possible system fallbacks:

1. pkg_check_modules is invoked, if `PGK_CONFIG ...` is present
2. find_package is invoked if `FIND_PACKAGE_OPTIONS` is present and `pkg_check_modules` has failed

If `ALWAYS_ALLOW_CONAN_FALLBACK` is present - `obey_system_dependencies` will be ignored for the package

Currently, the following dependencies are retrieved using Conan:

* zlib
* expat
* wxwidgets
* libmp3lame
* libid3tag
* libmad

The last three libraries are included in this commit, as they depend on zlib.
Properly pass **arch** and **os.version** to Conan

cmake-proxies/cmake-modules/dependencies/wxwidgets.cmake

@@ -0,0 +1,94 @@
+if( ${_OPT}use_wxwidgets STREQUAL "system" ) 
+    if( NOT TARGET wxwidgets::wxwidgets )
+        add_library( wxwidgets::wxwidgets INTERFACE IMPORTED GLOBAL)
+    endif()
+    
+    if( NOT TARGET wxwidgets::base )
+        add_library( wxwidgets::base ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::core )
+        add_library( wxwidgets::core ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::html )
+        add_library( wxwidgets::html ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::xml )
+        add_library( wxwidgets::xml ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::xrc )
+        add_library( wxwidgets::xrc ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::qa )
+        add_library( wxwidgets::qa ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::aui )
+        add_library( wxwidgets::aui ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::adv )
+        add_library( wxwidgets::adv ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( NOT TARGET wxwidgets::wxwidgets )
+        add_library( wxwidgets::wxwidgets ALIAS wxwidgets::wxwidgets )
+    endif()
+
+    if( wxWidgets_INCLUDE_DIRS_NO_SYSTEM )
+        target_include_directories( wxwidgets::wxwidgets INTERFACE ${wxWidgets_INCLUDE_DIRS_NO_SYSTEM} )
+    else()
+        target_include_directories( wxwidgets::wxwidgets INTERFACE ${wxWidgets_INCLUDE_DIRS} )
+    endif() 
+
+    target_compile_definitions( wxwidgets::wxwidgets INTERFACE
+        ${wxWidgets_DEFINITIONS_GENERAL}
+        $<$<CONFIG:Debug>:
+            ${wxWidgets_DEFINITIONS_DEBUG}
+        >
+        $<$<NOT:$<CONFIG:Debug>>:
+            ${wxWidgets_DEFINITIONS_OPTIMIZED}
+        >
+    )
+
+    target_link_directories( wxwidgets::wxwidgets INTERFACE
+        $<$<PLATFORM_ID:Windows>:
+           ${wxWidgets_LIB_DIR}
+        >
+    )
+
+    target_link_libraries( wxwidgets::wxwidgets INTERFACE
+        ${wxWidgets_LIBRARIES}
+        $<$<NOT:$<PLATFORM_ID:Windows>>:
+           z
+        >
+    )
+
+    set( toolkit "${wxWidgets_LIBRARIES}" )
+
+    if( "${toolkit}" MATCHES ".*gtk2.*" )
+        set( gtk gtk+-2.0 )
+        set( glib glib-2.0 )
+    elseif( "${toolkit}" MATCHES ".*gtk3.*" )
+        set( gtk gtk+-3.0 )
+        set( glib glib-2.0 )
+    elseif( "${toolkit}" MATCHES ".*gtk4.*" )
+        set( gtk gtk+-4.0 )
+        set( glib glib-2.0 )
+    endif()
+endif()
+
+if( NOT CMAKE_SYSTEM_NAME MATCHES "Windows|Darwin" )
+
+    if( NOT DEFINED gtk )
+        set( gtk gtk+-2.0 )
+        set( glib glib-2.0 )
+    endif()
+
+    pkg_check_modules( GTK REQUIRED IMPORTED_TARGET GLOBAL ${gtk} )
+    pkg_check_modules( GLIB REQUIRED IMPORTED_TARGET GLOBAL ${glib} )
+endif()

cmake-proxies/cmake-modules/dependencies/zlib.cmake

@@ -0,0 +1,39 @@
+# ZLib is a very popular library to use.
+# Some of the dependecies do not check for the system libraries,
+# which can be problematic.
+# We need to call find_package once again.
+if (${_OPT}use_zlib STREQUAL "system")
+    message(STATUS "Fixing up ZLib mess...")
+    
+    find_package(ZLIB REQUIRED)
+
+    set_target_properties(ZLIB::ZLIB PROPERTIES
+        INTERFACE_INCLUDE_DIRECTORIES "${ZLIB_INCLUDE_DIRS}")
+
+    if(ZLIB_LIBRARY_RELEASE)
+        set_property(TARGET ZLIB::ZLIB APPEND PROPERTY
+            IMPORTED_CONFIGURATIONS RELEASE)
+        
+        set_property(TARGET ZLIB::ZLIB
+            PROPERTY INTERFACE_LINK_LIBRARIES 
+            "${ZLIB_LIBRARY_RELEASE}"
+        )
+    endif()
+
+    if(ZLIB_LIBRARY_DEBUG)
+        set_property(TARGET ZLIB::ZLIB APPEND PROPERTY
+            IMPORTED_CONFIGURATIONS DEBUG)
+
+        set_property(TARGET ZLIB::ZLIB
+            PROPERTY INTERFACE_LINK_LIBRARIES 
+            "${ZLIB_LIBRARY_DEBUG}"
+        )
+    endif()
+
+    if(NOT ZLIB_LIBRARY_RELEASE AND NOT ZLIB_LIBRARY_DEBUG)
+        set_property(TARGET ZLIB::ZLIB
+            PROPERTY INTERFACE_LINK_LIBRARIES 
+            "${ZLIB_LIBRARY}"
+        )
+    endif()
+endif()