Remove windows guard

Author: rupprecht

lldb/test/API/commands/settings/use_source_cache/Makefile

@@ -6,6 +6,4 @@ include Makefile.rules
 # Copy file into the build folder to enable the test to modify it.
 main-copy.cpp: main.cpp
 	cp -f $< $@
-ifneq "$(OS)" "Windows_NT"  # chmod is not available on Windows
 	chmod u+w $@
-endif