unix: adjust replacement regex for removed struct fields for linux/s390x

CL 87555 added the AT_STATX_* constants which are garbled on linux/s390x due
to the replacement regex in mkpost.go being too broad. Adjust the regex to
only match on word boundaries.

Change-Id: I898547fbbbc5d02965e86300e9144fb65207ab33
Reviewed-on: https://go-review.googlesource.com/87876Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/mkpost.go

@@ -72,7 +72,7 @@ func main() {
 		b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
 
 		// Remove padding, hidden, or unused fields
-		removeFieldsRegex = regexp.MustCompile(`X_\S+`)
+		removeFieldsRegex = regexp.MustCompile(`\bX_\S+`)
 		b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
 	}
 

unix/ztypes_linux_s390x.go

@@ -702,9 +702,9 @@ const (
 	AT_NO_AUTOMOUNT = 0x800
 	AT_REMOVEDIR    = 0x200
 
-	AT_STAT_ = 0x0
-	AT_STAT_ = 0x2000
-	AT_STAT_ = 0x4000
+	AT_STATX_SYNC_AS_STAT = 0x0
+	AT_STATX_FORCE_SYNC   = 0x2000
+	AT_STATX_DONT_SYNC    = 0x4000
 
 	AT_SYMLINK_FOLLOW   = 0x400
 	AT_SYMLINK_NOFOLLOW = 0x100