[LLDB] Skip random failing tests on Arm/AArch64 Linux bots

Following tests have been failing randomly on LLDB Arm and AArch64 Linux
builtbots:

TestMultilineNavigation.py
TestMultilineCompletion.py
TestIOHandlerCompletion.py
TestGuiBasic.py

I have increased allocated CPU resources to these bots but it has not
improved situation to an acceptable level. This patch marks them as
skipped on Arm/AArch64 for now.