CMake: Fix [qt-]configure[-module].bat arguments with backslashes

We must escape backslashes in CMake code that's to be evaluated and in
the arguments we read from config.opt.

Change-Id: I65d033c77f71888974983aa3d834acb2fe89f3fb
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtProcessConfigureArgs.cmake

@@ -44,6 +44,7 @@ endif()
 file(STRINGS "${OPTFILE}" configure_args)
 list(FILTER configure_args EXCLUDE REGEX "^[ \t]*$")
 list(TRANSFORM configure_args STRIP)
+list(TRANSFORM configure_args REPLACE "\\\\" "\\\\\\\\")
 unset(generator)
 set(auto_detect_generator TRUE)
 unset(device_options)
@@ -390,6 +391,7 @@ function(qt_call_function func)
         string(APPEND call_code "\"${ARGV${i}}\" ")
     endforeach()
     string(APPEND call_code ")")
+    string(REPLACE "\\" "\\\\" call_code "${call_code}")
     if(${CMAKE_VERSION} VERSION_LESS "3.18.0")
         set(incfile qt_tmp_func_call.cmake)
         file(WRITE "${incfile}" "${call_code}")