Debugger: Fall back to assembler in LLDB

... if source file does not exist. This is the same
logic as for GDB now.

Change-Id: I3e5a3273b571658b4dd4200c9b3a0e9542a16015
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/debugger/debuggerengine.h

@@ -100,6 +100,7 @@ public:
     void setNeedsRaise(bool on) { m_needsRaise = on; }
     void setNeedsMarker(bool on) { m_needsMarker = on; }
     void setFileName(const QString &fileName) { m_fileName = fileName; }
+    void setUseAssembler(bool on) { m_hasDebugInfo = !on; }
     bool needsRaise() const { return m_needsRaise; }
     bool needsMarker() const { return m_needsMarker; }
     bool hasDebugInfo() const { return m_hasDebugInfo; }