Teach LLVM-Config to use logical target names (2/2)

The module still needs to collect the list of all available libraries
in order to satisfy the 'all' component.  Provide this in the package
configuration file, 'LLVMConfig.cmake', as a LLVM_AVAILABLE_LIBS
variable.  (A variable is scoped better than a global property.)
Since this won't be set for our own build, fall back to looking up the
LLVM_LIBS property to get the value when it is not set.

Contributed by Brad King.

llvm-svn: 201853
diff --git a/llvm/cmake/modules/LLVMConfig.cmake.in b/llvm/cmake/modules/LLVMConfig.cmake.in
index c1b6450..11857a5 100644
--- a/llvm/cmake/modules/LLVMConfig.cmake.in
+++ b/llvm/cmake/modules/LLVMConfig.cmake.in
@@ -8,7 +8,7 @@
 
 set(LLVM_COMMON_DEPENDS @LLVM_COMMON_DEPENDS@)
 
-set_property( GLOBAL PROPERTY LLVM_LIBS "@llvm_libs@")
+set(LLVM_AVAILABLE_LIBS @LLVM_AVAILABLE_LIBS@)
 
 set(LLVM_ALL_TARGETS @LLVM_ALL_TARGETS@)