[lldb] Require x86 for unwind no-return test

The core file used is built for i386 so we
need the x86 backend to be able to load it.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D100195

lldb/test/API/functionalities/unwind/noreturn/module-end/TestNoReturnModuleEnd.py

@@ -15,6 +15,7 @@ class TestNoreturnModuleEnd(TestBase):
     NO_DEBUG_INFO_TESTCASE = True
     mydir = TestBase.compute_mydir(__file__)
 
+    @skipIfLLVMTargetMissing("X86")
     def test(self):
         target = self.dbg.CreateTarget("test.out")
         process = target.LoadCore("test.core")