[llvm] r280013 - [CMake] Make LLVMConfig.cmake variable names match in-tree names

[Brad King via llvm-commits]

On 08/29/2016 05:26 PM, Chris Bieneman via llvm-commits wrote:
> New Revision: 280013
> URL: http://llvm.org/viewvc/llvm-project?rev=280013&view=rev
[snip]
> This renames:
> LLVM_INCLUDE_DIRS -> LLVM_INCLUDE_DIR
> LLVM_LIBRARY_DIRS -> LLVM_LIBRARY_DIR
> 
> The versions ending in S are not used in-tree anywhere. This also
> cleans up LLVM_LIBRARY_DIR being set to the same value with and
> without the "S".

Please don't do this.  It breaks compatibility with existing consumers
of LLVM that build with CMake.  Also it breaks the convention documented
by CMake for public-facing package information variables:

 https://cmake.org/cmake/help/v3.6/manual/cmake-developer.7.html#standard-variable-names

The public-facing variables should be plural-named because they may have
zero, one, or more than one entries in a list.  Even if they happen to
have only one now they may have more in the future.

Thanks,
-Brad