Xfail TestCrashDuringStep and TestCreateDuringInstructionStep on arm-linux

Both of above tests fail on arm and bugs have been reported on android already.
Adding arm-linux decorator because android decorator doesnt xfail these test when run on linux. 

llvm-svn: 269647

lldb/packages/Python/lldbsuite/test/functionalities/thread/crash_during_step/TestCrashDuringStep.py

@@ -22,6 +22,7 @@ class CreateDuringStepTestCase(TestBase):
 
     @expectedFailureAll(oslist=["windows"], bugnumber="llvm.org/pr24778")
     @expectedFailureAndroid("llvm.org/pr24497", archs=['arm', 'aarch64'])
+    @expectedFailureAll(oslist=["linux"], archs=["arm"], bugnumber="llvm.org/pr24497")
     @expectedFailureAll(triple = re.compile('^mips'))    # IO error due to breakpoint at invalid address
     def test_step_inst_with(self):
         """Test thread creation during step-inst handling."""

lldb/packages/Python/lldbsuite/test/linux/thread/create_during_instruction_step/TestCreateDuringInstructionStep.py

@@ -23,6 +23,7 @@ class CreateDuringInstructionStepTestCase(TestBase):
 
     @skipUnlessPlatform(['linux'])
     @expectedFailureAndroid('llvm.org/pr24737', archs=['arm'])
+    @expectedFailureAll(oslist=["linux"], archs=["arm"], bugnumber="llvm.org/pr24737")
     def test_step_inst(self):
         self.build(dictionary=self.getBuildFlags())
         exe = os.path.join(os.getcwd(), "a.out")