Support cross-compiling the C++ tests for Windows

With built-in handling for MinGW.

Author: Ortham

ffi/CMakeLists.txt

@@ -10,7 +10,23 @@ elseif(WIN32)
     set(SYSTEM_LIBS ntdll ws2_32)
 endif()
 
-set(TARGET_PATH "${CMAKE_SOURCE_DIR}/../target")
+if(CMAKE_CROSSCOMPILING AND NOT DEFINED RUST_TARGET)
+    if(WIN32 AND MINGW AND CMAKE_SIZEOF_VOID_P EQUAL 8)
+        set(RUST_TARGET "x86_64-pc-windows-gnu")
+    elseif(WIN32 AND MINGW AND CMAKE_SIZEOF_VOID_P EQUAL 4)
+        set(RUST_TARGET "i686-pc-windows-gnu")
+    else()
+        message(FATAL_ERROR "Cross-compiling without RUST_TARGET set, and an appropriate value could not be set automatically!")
+    endif()
+endif()
+
+if(DEFINED RUST_TARGET)
+    message(STATUS "Building for Rust target ${RUST_TARGET}")
+    set(TARGET_PATH "${PROJECT_SOURCE_DIR}/../target/${RUST_TARGET}")
+else()
+    set(TARGET_PATH "${PROJECT_SOURCE_DIR}/../target")
+endif()
+
 set(LIBLOADORDER_FFI_LIB_NAME "${CMAKE_STATIC_LIBRARY_PREFIX}loadorder_ffi${CMAKE_STATIC_LIBRARY_SUFFIX}")
 
 add_library(libloadorder_ffi INTERFACE)