[cmake] Make libcxx(abi) a dependency when building in-tree clang for…

… macOS

As discussed on IRC this morning, when building an in-tree clang for
testing we have to have libcxx and libcxxabi checked out. This is a
common pitfall. Not only are the resulting failures non-obvious, they
only manifest when running the test suite, *after* building lldb and
clang. By making them a hard dependency (on macOS) we fail earlier with
a more useful error message.

Differential revision: https://reviews.llvm.org/D55837

llvm-svn: 349539

lldb/CMakeLists.txt

@@ -157,6 +157,10 @@ if(LLDB_INCLUDE_TESTS)
 
   if(TARGET clang)
     list(APPEND LLDB_TEST_DEPS clang)
+    if(APPLE)
+      list(APPEND LLDB_TEST_DEPS cxx)
+      list(APPEND LLDB_TEST_DEPS cxxabi)
+    endif()
   endif()
 
   if(TARGET dsymutil)