Check clean-compiler revision in Makefile

Makefile

-clean-compiler:
-	svn checkout -r 3056 https://svn.cs.ru.nl/repos/clean-compiler/branches/itask/ clean-compiler
+.ONESHELL:
+clean-compiler: .FORCE
+	REVISION=3061
+	cd clean-compiler; svn info | grep "Revision: $$REVISION" && exit 0
+	svn checkout -r $$REVISION https://svn.cs.ru.nl/repos/clean-compiler/branches/itask/ clean-compiler
 	$(MAKE) -j -C clean-compiler/main/Unix
 	$(MAKE) -j -C clean-compiler/backendC/CleanCompilerSources -f Makefile.linux64
 	ln -s ../../backendC/CleanCompilerSources/backend.a clean-compiler/backend/Clean\ System\ Files/backend_library
+
+.FORCE:
+
+.PHONY: .FORCE