[lldb] Fix build error in TestSimulatorPlatform.py
Before e5d08fcbac72 the Makefile would always compute the min-version,
even if it wasn't set in the triple. This nuance got lost when passing
the ARCH_CFLAGS directly from TestSimulatorPlatform.
JDevlieghere on Aug 21 2020, 1:33 PM.Authored by