[llvm] r242120 - [CMake] Unbreak add_llvm_external_project when external projects are specified.

[Chris Bieneman]

Brad,

Thank you for the clarification. This is most useful!

-Chris

> On Jul 14, 2015, at 10:04 AM, Brad King <brad.king at kitware.com> wrote:
> 
> On 07/14/2015 11:57 AM, Chris Bieneman wrote:
>> If PATH does have some impact on how the value is expanded
> 
> There is a subtle case where it does affect the value that was only
> documented recently:
> 
> http://www.cmake.org/cmake/help/v3.3/command/set.html
> "It is possible for the cache entry to exist prior to the call but
>  have no type set if it was created on the cmake(1) command line
>  by a user through the -D<var>=<value> option without specifying a
>  type. In this case the set command will add the type.
>  Furthermore, if the <type> is PATH or FILEPATH and the
>  <value> provided on the command line is a relative path, then the
>  set command will treat the path as relative to the current
>  working directory and convert it to an absolute path."
> 
> It has been that way for a long time and is implemented here:
> 
> http://www.cmake.org/gitweb?p=cmake.git;a=blob;f=Source/cmMakefile.cxx;hb=v3.3.0-rc4#l1754
> 
> but the above documentation was only added as of 3.3.
> 
> -Brad
>