Adding a hardware execution breakpoint with LLDB before lauching the target silently succeeds but it does not work

[xusheng6]

Due to #957, hardware execution breakpoint does NOT work on Linux with LLDB adapter. If the user attempts to add it during debugging, they will be met with the expected error message:

However, if the user does so before debugging, the breakpoint will be recorded, but then later when the lldb adapter tries to add them, it fails silently, which could cause confusion