[Polly][CMake] Fix lit setup for building the in the mono repo

Summary:
When building polly as part of the monorepo (actually, as part of any setup
using LLVM_ENABLE_PROJECTS), the LLVMPolly library used in the lit tests ends
up in a different directory in the build tree than in an in-tree build

Reviewers: Meinersbur, grosser, bollu

Reviewed By: Meinersbur

Subscribers: mgorny, bollu, pollydev, llvm-commits

Differential Revision: https://reviews.llvm.org/D44078

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@326702 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0cc33c3..cf6efd1 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -47,7 +47,11 @@
 set(LLVM_BINARY_DIR "${LLVM_BINARY_DIR}")
 set(LLVM_TOOLS_DIR "${LLVM_TOOLS_BINARY_DIR}")
 set(LLVM_LIBS_DIR "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}")
-set(POLLY_LIB_DIR "${POLLY_BINARY_DIR}/lib")
+if (CMAKE_LIBRARY_OUTPUT_DIRECTORY)
+  set(POLLY_LIB_DIR ${CMAKE_LIBRARY_OUTPUT_DIRECTORY})
+else()
+  set(POLLY_LIB_DIR "${POLLY_BINARY_DIR}/lib")
+endif()
 
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in