[lldb][test] Prevent TestqOffsets.py picking up host binaries (#157432)

Due to a fallback in GDBRemoteCommunicationClient.cpp, on Linux we will
assume a PID of 1 if the remote does not respond in some way that tells
us the real PID.

So if PID 1 happened to be a process that the current user could read,
we would try to debug that instead. On my current machine, PID 1 was
sshd run by root so we would ignore it. If I changed the fallback to
some process ID run by my user, the test would fail.

To prevent this, select the remote-linux platform before creating the
target. This means we won't attempt any host lookups.

Fixes #155895

Author: DavidSpickett

lldb/test/API/functionalities/gdb_remote_client/TestqOffsets.py

@@ -12,6 +12,8 @@ def qOffsets(self):
 
     def test(self):
         self.server.responder = TestqOffsets.Responder()
+        # This ensures that we do not pick up any binaries on the host.
+        self.runCmd("platform select remote-linux")
         target = self.createTarget("qOffsets.yaml")
         text = target.modules[0].FindSection(".text")
         self.assertEqual(text.GetLoadAddress(target), lldb.LLDB_INVALID_ADDRESS)