Update a reg entry for WinGHCi

* hptool/os-extras/win/templates/Nsisfile.nsi.mu
  * winGHCi adds some reg entries when it is run, and one
    "WorkdingDir", it reads but never updates if it already
    exists, causing winGHCi associated with any newer HP
    installs to use an old value. So, create and remove this
    particular entry when we do the install.

Author: randen

hptool/os-extras/win/templates/Nsisfile.nsi.mu

@@ -289,6 +289,8 @@ Section "Store GHC's location in registry" SecGHCLoc
   WriteRegStr HKCU "Software\Haskell\GHC\ghc-${GHC_VERSION}" "InstallDir" "$INSTDIR"
   WriteRegStr HKCU "Software\Haskell\GHC" "InstallDir" "$INSTDIR"
 
+  WriteRegStr HKCU "Software\Haskell\WinGHCi 1.0.6" "WorkingDir" "$INSTDIR\winghci"
+
 SectionEnd
 
 Section "Create uninstaller" SecAddRem
@@ -397,6 +399,8 @@ Section "Uninstall"
 
   DeleteRegKey HKCU "Software\Haskell\GHC\ghc-${GHC_VERSION}"
   DeleteRegKey HKCU "Software\Haskell\GHC"
+  ; remove WorkingDir but keep any user customizations for winGHCi
+  DeleteRegValue HKCU "Software\Haskell\WinGHCi 1.0.6" "WorkingDir"
   DeleteRegKey HKLM "${PRODUCT_DIR_REG_KEY}"
   DeleteRegKey /IfEmpty HKCU Software\Haskell
   DeleteRegKey HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\HaskellPlatform-${PLATFORM_VERSION}"