Partially revert "[NFCI][lldb][test][asm] Enable AT&T syntax explicitly (#166770)" (#172233)
Flag changes reverted as those require the X86 target to be enabled.
Don't have time to test fixes as I need to go to sleep so will revert for now.
Reverts: 423919d31f4b55f22b09cd5066534f7c91e71d4b