cmd/ld: always set timestamp in PE header to 0

Fixes #9756.

Change-Id: If4ee6fe10f8f90294ff9c5e7480371494094b111
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/3740Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

doc/go1.5.txt

@@ -19,6 +19,7 @@ testing/quick: support generation of arrays (https://golang.org/cl/3865)
 Tools:
 
 cmd/vet: better validation of struct tags (https://golang.org/cl/2685)
+cmd/ld: no longer record build timestamp in Windows PE file header (https://golang.org/cl/3740)
 
 Performance:
 

src/cmd/ld/pe.c

@@ -646,7 +646,9 @@ asmbpe(void)
 	addpersrc();
 
 	fh.NumberOfSections = nsect;
-	fh.TimeDateStamp = time(0);
+	// Being able to produce identical output for identical input is
+	// much more beneficial than having build timestamp in the header.
+	fh.TimeDateStamp = 0;
 	fh.Characteristics = IMAGE_FILE_RELOCS_STRIPPED|
 		IMAGE_FILE_EXECUTABLE_IMAGE|IMAGE_FILE_DEBUG_STRIPPED;
 	if (pe64) {