Disable tools when cross-compiling

This is maintenance code that is only useful when actually runable on the
host.

CMakeLists.txt

@@ -42,8 +42,10 @@ endif()
 find_package(ZLIB REQUIRED)
 find_package(OsmTools)
 set_package_properties(OsmTools PROPERTIES TYPE OPTIONAL PURPOSE "Needed only for regenereating line metadata tables (you don't need this for distribution)")
-find_package(PolyClipping)
-set_package_properties(PolyClipping PROPERTIES TYPE OPTIONAL PURPOSE "Needed only for processing coverage area data from the Transport API Repository (you don't need this for distribution)")
+if (NOT CMAKE_CROSSCOMPILING)
+    find_package(PolyClipping)
+    set_package_properties(PolyClipping PROPERTIES TYPE OPTIONAL PURPOSE "Needed only for processing coverage area data from the Transport API Repository (you don't need this for distribution)")
+endif()
 
 if (NOT WIN32)
     find_package(Protobuf)

src/CMakeLists.txt

@@ -12,6 +12,6 @@ add_subdirectory(qmlplugin)
 if (TARGET Qt5::Quick)
     add_subdirectory(quick)
 endif()
-if (NOT CROSS_COMPILING)
+if (NOT CMAKE_CROSSCOMPILING)
     add_subdirectory(tools)
 endif()