[compiler-rt] Use the correct minimum version flag for simulators on Apple

platforms.

For the simulators this changes the following compilation flags (
used both for building the runtime and lit tests).

iOS simulator: `-miphoneos-version-min` -> `-mios-simulator-version-min`
watchOS simulator: `-mwatchos-version-min` -> `-mwatchos-simulator-version-min`
tvOS simulator: `-mtvos-version-min` -> `-mtvos-simulator-version-min`

rdar://problem/59463146