Add support for archives with no symbol table or string table.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185664 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Object/Inputs/archive-test.a-gnu-minimal b/test/Object/Inputs/archive-test.a-gnu-minimal
new file mode 100644
index 0000000..a243273
--- /dev/null
+++ b/test/Object/Inputs/archive-test.a-gnu-minimal
@@ -0,0 +1,2 @@
+!<arch>
+test/           1372964340  1000  1000  100664  0         `