checkpatch: emit an error when using predefined timestamp macros

Since commit fe7c36c7 ("Makefile: Build with -Werror=date-time if
the compiler supports it"), use of __DATE__, __TIME__, and __TIMESTAMP__
has not been allowed.

As this test is gcc version specific (> 4.9), it hasn't prevented a few
new uses from creeping into the kernel sources.

Make checkpatch complain about them.
Signed-off-by: NJoe Perches <joe@perches.com>
Original-patch-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -5089,6 +5089,12 @@ sub process {
 			}
 		}
 
+# check for uses of __DATE__, __TIME__, __TIMESTAMP__
+		while ($line =~ /\b(__(?:DATE|TIME|TIMESTAMP)__)\b/g) {
+			ERROR("DATE_TIME",
+			      "Use of the '$1' macro makes the build non-deterministic\n" . $herecurr);
+		}
+
 # check for use of yield()
 		if ($line =~ /\byield\s*\(\s*\)/) {
 			WARN("YIELD",