libct/dmz: Move comment out of the Makefile rule

Otherwise it is shown when compiling, like this:
	# We use the flags suggested in nolibc/nolibc.h, it makes the binary very small.
	gcc  -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib -lgcc -static -o runc-dmz _dmz.c
	strip -gs runc-dmz

Having it before the target is equally clear and will not be shown while
compiling.

Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>

libcontainer/dmz/Makefile

@@ -1,7 +1,7 @@
 # Get CC values for cross-compilation.
 include ../../cc_platform.mk
 
+# We use the flags suggested in nolibc/nolibc.h, it makes the binary very small.
 runc-dmz: _dmz.c
-	# We use the flags suggested in nolibc/nolibc.h, it makes the binary very small.
 	$(CC) $(CFLAGS) -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib -lgcc -static -o $@ $^
 	$(STRIP) -gs $@