convert paths to native paths under Windows

CMake/cotire.cmake

@@ -889,6 +889,9 @@ function (cotire_init_compile_cmd _cmdVar _language _compilerLauncher _compilerE
 	if (NOT _compilerArg1)
 		set (_compilerArg1 ${CMAKE_${_language}_COMPILER_ARG1})
 	endif()
+	if (WIN32 AND CMAKE_${_language}_COMPILER_ID MATCHES "MSVC|Intel")
+		file (TO_NATIVE_PATH "${_compilerExe}" _compilerExe)
+	endif()
 	string (STRIP "${_compilerArg1}" _compilerArg1)
 	if ("${CMAKE_GENERATOR}" MATCHES "Make|Ninja")
 		# compiler launcher is only supported for Makefile and Ninja
@@ -1246,7 +1249,15 @@ function (cotire_scan_includes _includesVar)
 		set (${_includesVar} "" PARENT_SCOPE)
 		return()
 	endif()
-	list (APPEND _cmd ${_existingSourceFiles})
+	# add source files to be scanned
+	if (WIN32 AND "${_option_COMPILER_ID}" MATCHES "MSVC|Intel")
+		foreach (_sourceFile ${_existingSourceFiles})
+			file (TO_NATIVE_PATH "${_sourceFile}" _sourceFileNative)
+			list (APPEND _cmd "${_sourceFileNative}")
+		endforeach()
+	else()
+		list (APPEND _cmd ${_existingSourceFiles})
+	endif()
 	if (COTIRE_VERBOSE)
 		message (STATUS "execute_process: ${_cmd}")
 	endif()