[LLD][ELF] - Add a test for "unbalanced --push-state/--pop-state" error.

We had no such test.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@347552 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/ELF/push-state.s b/test/ELF/push-state.s
index 5a01cd2..f3d55c3 100644
--- a/test/ELF/push-state.s
+++ b/test/ELF/push-state.s
@@ -32,5 +32,8 @@
 // RUN: ld.lld -o %t.exe -L%t.dir -push-state -static -pop-state  %t1.o -lfoo
 // RUN: not ld.lld -o %t.exe -L%t.dir -push-state -static %t1.o -lfoo
 
+// RUN: not ld.lld -o %t.exe -pop-state %t.a %t1.o -M 2>&1 | FileCheck -check-prefix=ERR %s
+// ERR: error: unbalanced --push-state/--pop-state
+
 .globl _start
 _start: