CMakeModules: Add MinGWClangCross

Facilitates what programs we need for cross-compiling to Windows from
Linux using LLVM's compilers. Based on MinGWCross

CMakeModules/MinGWClangCross.cmake

@@ -0,0 +1,55 @@
+set(MINGW_PREFIX                /usr/x86_64-w64-mingw32/)
+set(CMAKE_SYSTEM_NAME           Windows)
+set(CMAKE_SYSTEM_PROCESSOR      x86_64)
+
+set(CMAKE_FIND_ROOT_PATH        ${MINGW_PREFIX})
+set(SDL2_PATH                   ${MINGW_PREFIX})
+set(MINGW_TOOL_PREFIX           ${CMAKE_SYSTEM_PROCESSOR}-w64-mingw32-)
+
+# Specify the cross compiler
+set(CMAKE_C_COMPILER            ${MINGW_TOOL_PREFIX}clang)
+set(CMAKE_CXX_COMPILER          ${MINGW_TOOL_PREFIX}clang++)
+set(CMAKE_RC_COMPILER           ${MINGW_TOOL_PREFIX}windres)
+set(CMAKE_C_COMPILER_AR         ${MINGW_TOOL_PREFIX}ar)
+set(CMAKE_CXX_COMPILER_AR       ${MINGW_TOOL_PREFIX}ar)
+set(CMAKE_C_COMPILER_RANLIB     ${MINGW_TOOL_PREFIX}ranlib)
+set(CMAKE_CXX_COMPILER_RANLIB   ${MINGW_TOOL_PREFIX}ranlib)
+
+# Mingw tools
+set(STRIP                       ${MINGW_TOOL_PREFIX}strip)
+set(WINDRES                     ${MINGW_TOOL_PREFIX}windres)
+set(ENV{PKG_CONFIG}             ${MINGW_TOOL_PREFIX}pkg-config)
+
+# ccache wrapper
+option(USE_CCACHE "Use ccache for compilation" OFF)
+if(USE_CCACHE)
+    find_program(CCACHE ccache)
+    if(CCACHE)
+        message(STATUS "Using ccache found in PATH")
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ${CCACHE})
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ${CCACHE})
+    else(CCACHE)
+        message(WARNING "USE_CCACHE enabled, but no ccache found")
+    endif(CCACHE)
+endif(USE_CCACHE)
+
+# Search for programs in the build host directories
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+
+
+# Echo modified cmake vars to screen for debugging purposes
+if(NOT DEFINED ENV{MINGW_DEBUG_INFO})
+        message("")
+        message("Custom cmake vars: (blank = system default)")
+        message("-----------------------------------------")
+        message("* CMAKE_C_COMPILER                     : ${CMAKE_C_COMPILER}")
+        message("* CMAKE_CXX_COMPILER                   : ${CMAKE_CXX_COMPILER}")
+        message("* CMAKE_RC_COMPILER                    : ${CMAKE_RC_COMPILER}")
+        message("* WINDRES                              : ${WINDRES}")
+        message("* ENV{PKG_CONFIG}                      : $ENV{PKG_CONFIG}")
+        message("* STRIP                                : ${STRIP}")
+        message("* USE_CCACHE                           : ${USE_CCACHE}")
+        message("")
+        # So that the debug info only appears once
+        set(ENV{MINGW_DEBUG_INFO} SHOWN)
+endif()