[LLVMdev] Can't build against LLVM-3.5 with CMake: CMakeExports.cmake broken?

[Dan Liew]

Hi David,

CC'ing Brad King and Eric Christopher as they'll probably be interested.

I've just managed to reproduce your issue David. I figured this out
because my Linux distribution just upgraded to LLVM/Clang 3.5 and I
noticed that trying use find_package(LLVM ...) was broken :( . They
use the Autoconf/Makefile build system (specifically because the CMake
build system doesn't support generating a single versioned shared
library) and use --enable-shared flag to configure.

What is happening is that none of the libraries are being added into
LLVMExports.cmake file when it is generated by
``cmake/modules/Makefile``. So when a CMake project tries to use
``find_package()`` it complains about the missing targets.

This is happening because the ``LLVMConfigLibs`` makefile variable is
empty when used in ``cmake/modules/Makefile``. It is normally set in
Makefile.rules . However if you build with --enable-shared this
variable doesn't get set and so LLVMExports.cmake isn't generated
correctly.

@David: Were you also compiling this way?

One way to "fix" this is make sure LLVMConfigLibs is also set when
using --enable-shared as the attached patch does. I'm not convinced
this is the right way to do it though. Perhaps
``cmake/modules/Makefile`` should invoke llvm-config itself?

This is rather annoying. I didn't catch this before because when I was
testing I never used --enable-shared.

Thoughts?

Thanks,
Dan.
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