Add ECLIPSE_CDT4_GENERATE_SOURCE_PROJECT as a ADVANCED cache variable (#9631)

This variable has been supported since 2.6 I think, having it in the cache
makes it easier to use (see bug report #9631)

Alex

Modules/CMakeFindEclipseCDT4.cmake

@@ -20,6 +20,10 @@ FIND_PROGRAM(CMAKE_ECLIPSE_EXECUTABLE NAMES eclipse DOC "The Eclipse executable"
 # This variable is used by the Eclipse generator and appended to the make invocation commands.
 SET(CMAKE_ECLIPSE_MAKE_ARGUMENTS "" CACHE STRING "Additional command line arguments when Eclipse invokes make. Enter e.g. -j<some_number> to get parallel builds")
 
+# This variable is used by the Eclipse generator in out-of-source builds only.
+SET(ECLIPSE_CDT4_GENERATE_SOURCE_PROJECT FALSE CACHE BOOL "If enabled, CMake will generate a source project for Eclipse in CMAKE_SOURCE_DIR")
+MARK_AS_ADVANCED(ECLIPSE_CDT4_GENERATE_SOURCE_PROJECT)
+
 # The Eclipse generator needs to know the standard include path
 # so that Eclipse ca find the headers at runtime and parsing etc. works better
 # This is done here by actually running gcc with the options so it prints its