common: don't store gzip timestamps

This makes the build reproducible.

doc/Makefile

@@ -233,7 +233,7 @@ $(MANPAGES_WEBDIR_LINUX) $(MANPAGES_WEBDIR_WINDOWS):
 	man ./$< > $@
 
 %.gz: %
-	gzip -c ./$* > $@
+	gzip -nc ./$* > $@
 
 %.html: %
 	groff -mandoc -Thtml ./$< > $@

src/tools/Makefile.inc

-# Copyright 2014-2019, Intel Corporation
+# Copyright 2014-2020, Intel Corporation
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
@@ -283,7 +283,7 @@ endif
 endif
 
 %.gz: %
-	gzip -c ./$< > $@
+	gzip -nc ./$< > $@
 
 %.txt: %
 	man ./$< > $@