cmd/link: enable DEP for Windows executables

There's no reason not to enable DEP in 2019, especially given Go's
minimum operating system level.

RELNOTE=yes

Change-Id: I9c3bbc5b05a1654876a218123dd57b9c9077b780
Reviewed-on: https://go-review.googlesource.com/c/go/+/203601Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/cmd/link/internal/ld/lib.go

@@ -1188,6 +1188,9 @@ func (ctxt *Link) hostlink() {
 		// ancient compatibility hacks.
 		argv = append(argv, "-Wl,--tsaware")
 
+		// Enable DEP
+		argv = append(argv, "-Wl,--nxcompat")
+
 		argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
 		argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
 		argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))

src/cmd/link/internal/ld/pe.go

@@ -861,14 +861,18 @@ func (f *peFile) writeOptionalHeader(ctxt *Link) {
 
 	switch ctxt.Arch.Family {
 	case sys.ARM:
-		oh64.DllCharacteristics = IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE | IMAGE_DLLCHARACTERISTICS_NX_COMPAT
-		oh.DllCharacteristics = IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE | IMAGE_DLLCHARACTERISTICS_NX_COMPAT
+		oh64.DllCharacteristics = IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE
+		oh.DllCharacteristics = IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE
 	}
 
 	// Mark as having awareness of terminal services, to avoid ancient compatibility hacks.
 	oh64.DllCharacteristics |= IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE
 	oh.DllCharacteristics |= IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE
 
+	// Enable DEP
+	oh64.DllCharacteristics |= IMAGE_DLLCHARACTERISTICS_NX_COMPAT
+	oh.DllCharacteristics |= IMAGE_DLLCHARACTERISTICS_NX_COMPAT
+
 	// Disable stack growth as we don't want Windows to
 	// fiddle with the thread stack limits, which we set
 	// ourselves to circumvent the stack checks in the