CMake: Support cross-compiling

This relies on a working cross-compiler, of course, as well as a separate build
directory for cross-compiled builds, with DFHACK_NATIVE_BUILD_DIR pointing
to an already-successful native build directory (this is needed for protoc).

CMakeLists.txt

@@ -58,6 +58,11 @@ if(MSVC)
 add_definitions( "/wd4819" )
 endif()
 
+IF(CMAKE_CROSSCOMPILING)
+  SET(DFHACK_NATIVE_BUILD_DIR "DFHACK_NATIVE_BUILD_DIR-NOTFOUND" CACHE FILEPATH "Path to a native build directory")
+  INCLUDE("${DFHACK_NATIVE_BUILD_DIR}/ImportExecutables.cmake")
+ENDIF()
+
 # set up folder structures for IDE solutions
 # MSVC Express won't load solutions that use this. It also doesn't include MFC supported
 # Check for MFC!

depends/protobuf/CMakeLists.txt

@@ -22,7 +22,12 @@ IF(CMAKE_COMPILER_IS_GNUCC)
         FOREACH(namespace std::tr1 std )
             IF(HAVE_HASH_MAP EQUAL 0 AND NOT STL_HASH_OLD_GCC)
                 CONFIGURE_FILE("${CMAKE_CURRENT_SOURCE_DIR}/testHashMap.cpp.in" "${CMAKE_CURRENT_SOURCE_DIR}/testHashMap.cpp")
-                TRY_RUN(HASH_MAP_RUN_RESULT HASH_MAP_COMPILE_RESULT ${PROJECT_BINARY_DIR}/CMakeTmp "${CMAKE_CURRENT_SOURCE_DIR}/testHashMap.cpp")
+                IF(CMAKE_CROSSCOMPILING)
+                    TRY_COMPILE(HASH_MAP_COMPILE_RESULT ${PROJECT_BINARY_DIR}/CMakeTmp "${CMAKE_CURRENT_SOURCE_DIR}/testHashMap.cpp")
+                    SET(HASH_MAP_RUN_RESULT ${HASH_MAP_COMPILE_RESULT})
+                ELSE()
+                    TRY_RUN(HASH_MAP_RUN_RESULT HASH_MAP_COMPILE_RESULT ${PROJECT_BINARY_DIR}/CMakeTmp "${CMAKE_CURRENT_SOURCE_DIR}/testHashMap.cpp")
+                ENDIF()
                 IF (HASH_MAP_COMPILE_RESULT AND HASH_MAP_RUN_RESULT EQUAL 1)
                     SET(HASH_MAP_H <${header}>)
                     STRING(REPLACE "map" "set" HASH_SET_H ${HASH_MAP_H})
@@ -237,8 +242,12 @@ TARGET_LINK_LIBRARIES(protoc protobuf)
 
 # Protobuf compiler executable
 
-ADD_EXECUTABLE(protoc-bin google/protobuf/compiler/main.cc google/protobuf/compiler/command_line_interface.h google/protobuf/compiler/cpp/cpp_generator.h)
-IDE_FOLDER(protoc-bin "Depends")
+IF(NOT CMAKE_CROSSCOMPILING)
+    ADD_EXECUTABLE(protoc-bin google/protobuf/compiler/main.cc google/protobuf/compiler/command_line_interface.h google/protobuf/compiler/cpp/cpp_generator.h)
+    IDE_FOLDER(protoc-bin "Depends")
 
-SET_TARGET_PROPERTIES(protoc-bin PROPERTIES OUTPUT_NAME protoc)
-TARGET_LINK_LIBRARIES(protoc-bin protoc)
+    SET_TARGET_PROPERTIES(protoc-bin PROPERTIES OUTPUT_NAME protoc)
+    TARGET_LINK_LIBRARIES(protoc-bin protoc)
+
+    EXPORT(TARGETS protoc-bin FILE ${CMAKE_BINARY_DIR}/ImportExecutables.cmake )
+ENDIF()