Update ABIMacOSX_arm::PrepareTrivialCall to correctly align the stack pointer for apple's armv7 ABI.  When in a frameless function or in a prologue/epilogue where sp wasn't properly aligned, we could try to make function calls with an unaligned sp; the expression would crash.
Update ABIMacOSX_arm::PrepareTrivialCall to correctly align the
stack pointer for apple's armv7 ABI.  When in a frameless function
or in a prologue/epilogue where sp wasn't properly aligned, we could
try to make function calls with an unaligned sp; the expression
would crash.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@314265 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit f1ab65ae031203178442206331929b9975208050)

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb