[Sanitizers][Darwin] Allows '-mtargetos' to used to set minimum deployment target.

Currently, m{platform}-version-min is default flag used to set min deployment target within compilter-rt and sanitizers.
However, clang uses flags -target and -mtargetos for setting target triple and minimum deployment targets.
-mtargetos will be the preferred flag to set min version in the future and the
${platform}-version-min flag will not be used for future platforms.

This change allows darwin platforms to use either ${platform}-min-version or -mtargetos
without breaking lit test flags that allows for overriding the default min value in lit tests
Tests using flags: 'darwin_min_target_with_tls_support', 'min_macos_deployment_target'
will no longer fail if they use mtargetos instead of version-min.

rdar://81028225

Differential Revision: https://reviews.llvm.org/D130542