In one of the 2 places the LC_BUILD_VERSION load command is handled, there
is a bug preventing us from actually handling them (the address where to
read the load command was not updated). This patch factors reading the
deployment target load commands into a helper and adds testing for the 2
code paths calling the helper.
The testing is a llittle bit complicated because the only times those load
commands matter is when debugging a simulator process. I added a new
decorator to check that a specific SDK is available. The actual testing was
fairly easy once I knew how to run a simulated process.
Adding Pavel as a reviewer given I slightly modified the lldb-server test