[CMake] Change cpack install folder

[Totte Karlsson]

>> How can I get my nsis installer to install my distribution to
>> c:\myPackageName instead of C:\Program Files\myPackageName ?
>>
> NSIS installer does offer you the choice during installation right?
Yes.

> 1) Do you want to provide an alternate default choice?
Thats it.


> for 1) Normally you should set
> CPACK_PACKAGING_INSTALL_PREFIX
> and/or CPACK_PACKAGE_INSTALL_DIRECTORY

I tried setting
set(CPACK_PACKAGING_INSTALL_PREFIX		"C:\\")
but gets errors.
I also tried
set(CPACK_PACKAGING_INSTALL_PREFIX		"C:\\\\")
and that removed the errors. However, the installer still  first points to 
C:\\Program Files\\

> but do not know whether if NSIS honors those two vars.
Seem not. :(

But I found this NSIS specific setting
CPACK_NSIS_INSTALL_ROOT
But setting that as C:\\ still create the error: "Function missing ending ")" ".

Not sure how to get this one right..

-totte