Fix a bug in the lit test suite generation.

I'm not sure why this has to be CMAKE_CURRENT_SOURCE_DIR, but
it causes all kinds of strange cmake generation errors when it's
the binary dir.

llvm-svn: 346035
diff --git a/lldb/lit/CMakeLists.txt b/lldb/lit/CMakeLists.txt
index c91535b..657571d 100644
--- a/lldb/lit/CMakeLists.txt
+++ b/lldb/lit/CMakeLists.txt
@@ -83,6 +83,6 @@
 endif()
 
 add_lit_testsuites(LLDB
-  ${CMAKE_CURRENT_BINARY_DIR}
+  ${CMAKE_CURRENT_SOURCE_DIR}
   DEPENDS ${LLDB_TEST_DEPS}
   )