[llvm-config] Add --ignore-libllvm

This flag forces off linking libLLVM. This should resolve some issues reported on llvm-commits.

llvm-svn: 289605
diff --git a/llvm/tools/llvm-config/llvm-config.cpp b/llvm/tools/llvm-config/llvm-config.cpp
index 4b4a3ea..6fdc304 100644
--- a/llvm/tools/llvm-config/llvm-config.cpp
+++ b/llvm/tools/llvm-config/llvm-config.cpp
@@ -215,6 +215,7 @@
   --shared-mode     Print how the provided components can be collectively linked (`shared` or `static`).\n\
   --link-shared     Link the components as shared libraries.\n\
   --link-static     Link the component libraries statically.\n\
+  --ignore-libllvm  Ignore libLLVM and link component libraries instead.\n\
 Typical components:\n\
   all               All LLVM libraries (default).\n\
   engine            Either a native JIT or a bitcode interpreter.\n";
@@ -553,6 +554,8 @@
         LinkMode = LinkModeShared;
       } else if (Arg == "--link-static") {
         LinkMode = LinkModeStatic;
+      } else if (Arg == "--ignore-libllvm") {
+        LinkDyLib = false;
       } else {
         usage();
       }