Fix the checks for the Cygwin path.

I.e., do

	if we have 32-bit Cygwin
		CYGWIN_PATH=path to it
	else if we have 64-bit Cygwin
		CYGWIN_PATH=path to it
	else
		fail
	endif

rather than

	CYGWIN_PATH=standard path for 32-bit Cygwin
	if we don't have 32-bit cygwin and we do have 64-bit Cygwin
		CYGWIN_PATH=path to 64-bit cygwin
	else
		fail
	endif

as the latter will fail if we *do* have 32-bit Cygwin.

Change-Id: I42d607a1319263edcc1d6e546b813862b7d33ffa
Reviewed-on: https://code.wireshark.org/review/2756
Reviewed-by: Guy Harris <guy@alum.mit.edu>