git-gui: fix shortcut creation on cygwin

When the user tried to create a desktop icon with git gui on cygwin
wscript was complaining about an unknown option and displaying the
non-native path as such.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>

lib/win32.tcl

@@ -18,9 +18,9 @@ proc win32_create_lnk {lnk_path lnk_exec lnk_dir} {
 	eval [list exec wscript.exe \
 		/E:jscript \
 		/nologo \
-		[file join $oguilib win32_shortcut.js] \
+		[file nativename [file join $oguilib win32_shortcut.js]] \
 		$lnk_path \
-		[file join $oguilib git-gui.ico] \
+		[file nativename [file join $oguilib git-gui.ico]] \
 		$lnk_dir \
 		$lnk_exec] $lnk_args
 }