[WebAssembly] Only run WebAssembly objdump tests if it is enabled as a target

Differential Revision: https://reviews.llvm.org/D34712

llvm-svn: 306464
diff --git a/llvm/test/tools/llvm-objdump/WebAssembly/lit.local.cfg b/llvm/test/tools/llvm-objdump/WebAssembly/lit.local.cfg
new file mode 100644
index 0000000..0dd8c92
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/WebAssembly/lit.local.cfg
@@ -0,0 +1,2 @@
+if 'WebAssembly' not in config.root.targets:
+    config.unsupported = True