Double output after Ctrl+C on Windows
```
C:\Temp>type Test.hs
import Control.Exception
import System.Cmd
main = system "sleep 1m" `finally` putStrLn "goodbye"
C:\Temp>ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.10.1
C:\Temp>ghc --make Test.hs
[1 of 1] Compiling Main ( Test.hs, Test.o )
Linking Test.exe ...
C:\Temp>test.exe
^Cgoodbye
goodbye
C:\Temp>
```
The `^C` is the consoles way of saying that Ctrl+C was pressed - i.e. I ran the program and hit Ctrl+C while the sleep was still ongoing. I can replicate this issue from the DOS prompt and from the Cygwin prompt. It does not occur from GHCi.
<details><summary>Trac metadata</summary>
| Trac field | Value |
| ---------------------- | -------------- |
| Version | 6.10.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Runtime System |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture | |
</details>
<!-- {"blocked_by":[],"summary":"Finally run twice on Ctrl+C","status":"New","operating_system":"","component":"Runtime System","related":[],"milestone":"","resolution":"Unresolved","owner":{"tag":"Unowned"},"version":"6.10.1","keywords":[],"differentials":[],"test_case":"","architecture":"","cc":[""],"type":"Bug","description":"{{{\r\nC:\\Temp>type Test.hs\r\nimport Control.Exception\r\nimport System.Cmd\r\nmain = system \"sleep 1m\" `finally` putStrLn \"goodbye\"\r\n\r\nC:\\Temp>ghc --version\r\nThe Glorious Glasgow Haskell Compilation System, version 6.10.1\r\n\r\nC:\\Temp>ghc --make Test.hs\r\n[1 of 1] Compiling Main ( Test.hs, Test.o )\r\nLinking Test.exe ...\r\n\r\nC:\\Temp>test.exe\r\n^Cgoodbye\r\ngoodbye\r\nC:\\Temp>\r\n}}}\r\n\r\nThe {{{^C}}} is the consoles way of saying that Ctrl+C was pressed - i.e. I ran the program and hit Ctrl+C while the sleep was still ongoing. I can replicate this issue from the DOS prompt and from the Cygwin prompt. It does not occur from GHCi.","type_of_failure":"OtherFailure","blocking":[]} -->
issue