CheckSubmodules: Workaround submodules failing (#5222)

Workaround git's inability to recover from a shallow clone

cmake/modules/CheckSubmodules.cmake

@@ -123,8 +123,10 @@ MACRO(GIT_SUBMODULE SUBMODULE_PATH FORCE_DEINIT FORCE_REMOTE FULL_CLONE)
 			WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
 			OUTPUT_QUIET
 		)
+		MESSAGE("--   Deleting ${CMAKE_SOURCE_DIR}/.git/${SUBMODULE_PATH}")
+		FILE(REMOVE_RECURSE "${CMAKE_SOURCE_DIR}/.git/modules/${SUBMODULE_PATH}")
 		# Recurse
-		GIT_SUBMODULE(${SUBMODULE_PATH} false false ${FULL_CLONE_FLAG})
+		GIT_SUBMODULE(${SUBMODULE_PATH} false false true)
 	ELSE()
 		# Try to use the depth switch
 		IF(NO_SHALLOW_CLONE OR GIT_VERSION_STRING VERSION_LESS "1.8.4")
@@ -179,11 +181,9 @@ FOREACH(_submodule ${SUBMODULE_LIST})
 		GIT_SUBMODULE("${_submodule}" false false false)
 
 		SET(COUNTED 0)
-		SET(COUNTING "")
 		# Handle edge-cases where submodule didn't clone properly or re-uses a non-empty directory
 		WHILE(NOT GIT_RESULT EQUAL 0 AND COUNTED LESS MAX_ATTEMPTS)
-			LIST(APPEND COUNTING "x")
-			LIST(LENGTH COUNTING COUNTED)
+			MATH(EXPR COUNTED "${COUNTED}+1")
 			SET(MISSING_COMMIT false)
 			FOREACH(_phrase ${MISSING_COMMIT_PHRASES})
 				IF("${GIT_MESSAGE}" MATCHES "${_phrase}")