runtime: do not explicitly exit on ctrl handler

The default ctrl+c handler should process exits in situations where it
makes sense, like console apps, but not in situations where it doesn't,
like libraries or services. Therefore, we should remove the exit(2) so
that the default handler is used for this. This also uses the more
proper windows exit code of STATUS_CONTROL_C_EXIT, with the base case
handler installed by KernelBase.dll. In particular, this helps in the
case of services, which previously would terminate when receiving
shutdown signals, instead of passing them onward to the service program.
In this CL, contrary to CL 244959, we do not need to special case
services with expensive detection algorithms, or rely on hard-coded
library/archive flags.

Fixes #40167.
Fixes #40074.

Change-Id: I9bf6ed6f65cefeff754d270aa33fa4df8d0b451f
Reviewed-on: https://go-review.googlesource.com/c/go/+/243597
Run-TryBot: Jason A. Donenfeld <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Alex Brainman <[email protected]>
Reviewed-by: Jason A. Donenfeld <[email protected]>

Author: zx2c4

src/runtime/os_windows.go

@@ -1010,11 +1010,6 @@ func ctrlhandler1(_type uint32) uint32 {
 	if sigsend(s) {
 		return 1
 	}
-	if !islibrary && !isarchive {
-		// Only exit the program if we don't have a DLL.
-		// See https://golang.org/issues/35965.
-		exit(2) // SIGINT, SIGTERM, etc
-	}
 	return 0
 }