LLVMExports.cmake: Exclude gtest since they are not installed.

FIXME: gtest might be included if external project could refer to the build tree.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201488 91177308-0d34-0410-b5e6-96231b3b80d8
LLVMExports.cmake: Add System libs $(LIBS) to LLVMSupport, corresponding to r201077.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201489 91177308-0d34-0410-b5e6-96231b3b80d8
llvmbuild: Exclude disabled targets from LLVMExports.cmake.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201490 91177308-0d34-0410-b5e6-96231b3b80d8