FIX(cmake): Don't set WORKING_DIRECTORY for ExternalProject_Add()

This is a workaround for a bug that appeared in a recent version of CMake.

WORKING_DIRECTORY prepends the specified path to a list instead of using it directly, resulting in:

cd /D D:\a\1\b\overlay\overlay_xcompile-prefix;D:\a\1\b\overlay\overlay_xcompile-prefix\src\overlay_xcompile-build

For reference, this causes the build to fail on Windows with the following error:

"The filename, directory name, or volume label syntax is incorrect."

This commit simply removes the parameter from the ExternalProject_Add() call, since the default working directory is perfectly fine.

overlay/CMakeLists.txt

@@ -172,7 +172,6 @@ if(64_BIT AND MSVC)
 				"-Dversion=${PROJECT_VERSION}"
 				${CMAKE_SOURCE_DIR}/overlay
 			CMAKE_GENERATOR_PLATFORM "Win32"
-			WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/overlay/overlay_xcompile-prefix
 			INSTALL_COMMAND ""
 		)
 	else()
@@ -194,7 +193,6 @@ if(64_BIT AND MSVC)
 				"-Dsymbols=${symbols}"
 				"-Dversion=${PROJECT_VERSION}"
 				${CMAKE_SOURCE_DIR}/overlay
-			WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/overlay/overlay_xcompile-prefix
 			INSTALL_COMMAND ""
 		)
 	endif()