[lldb] [test] Fix new signal tests to use remote-linux plugin

Hopefully this will fix OSX and Windows buildbots

Author: mgorny

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

@@ -426,6 +426,7 @@ def cont(self):
 
         self.server.responder = MyResponder()
 
+        self.runCmd("platform select remote-linux")
         target = self.createTarget("a.yaml")
         process = self.connect(target)
 
@@ -434,7 +435,6 @@ def cont(self):
         self.assertEqual(process.threads[0].GetStopDescription(100),
                          'signal SIGBUS')
 
-    @skipIfWindows
     def test_signal_lldb_old(self):
         class MyResponder(MockGDBServerResponder):
             def qSupported(self, client_supported):
@@ -454,6 +454,7 @@ def cont(self):
 
         self.server.responder = MyResponder()
 
+        self.runCmd("platform select remote-linux")
         target = self.createTarget("a.yaml")
         process = self.connect(target)
 
@@ -462,7 +463,6 @@ def cont(self):
         self.assertEqual(process.threads[0].GetStopDescription(100),
                          'signal SIGUSR1')
 
-    @skipIfWindows
     def test_signal_lldb(self):
         class MyResponder(MockGDBServerResponder):
             def qSupported(self, client_supported):
@@ -479,6 +479,7 @@ def cont(self):
 
         self.server.responder = MyResponder()
 
+        self.runCmd("platform select remote-linux")
         target = self.createTarget("a.yaml")
         process = self.connect(target)