[CMake] Fix Xcode build with LLVM_ENABLE_OBJLIB.
This amends chapuni's r246156 to handle an Xcode quirk, one even called out
in the CMake documentation:
Some native build systems may not like targets that have only object files,
so consider adding at least one real source file to any target that
references $<TARGET_OBJECTS:objlib>.
I've limited the scope of this hack to Xcode for now.
llvm-svn: 247305
diff --git a/llvm/cmake/dummy.cpp b/llvm/cmake/dummy.cpp
new file mode 100644
index 0000000..c4e7e95
--- /dev/null
+++ b/llvm/cmake/dummy.cpp
@@ -0,0 +1 @@
+typedef int dummy;