Advertise 32 bit support for PlatformRemoteGDBServer on 64 bit systems.

[chaoren]

Add some error checking.

[clayborg]

Looks good.

lldb/trunk/source/Plugins/Platform/gdb-server/PlatformRemoteGDBServer.cpp

 {
 }
 
 bool
 PlatformRemoteGDBServer::GetSupportedArchitectureAtIndex (uint32_t idx, ArchSpec &arch)
 {
     ArchSpec remote_arch = m_gdb_client.GetSystemArchitecture();
 
-    // TODO: 64 bit systems should also advertize support for 32 bit arch
-    // unknown CPU, we just support the one arch
     if (idx == 0)
     {
         arch = remote_arch;
-        return true;
+        return arch.IsValid();
+    }
+    else if (idx == 1 && remote_arch.IsValid() && remote_arch.GetTriple().isArch64Bit())
+    {
+        arch.SetTriple(remote_arch.GetTriple().get32BitArchVariant());
+        return arch.IsValid();
     }
     return false;
 }
 
 size_t
 PlatformRemoteGDBServer::GetSoftwareBreakpointTrapOpcode (Target &target, BreakpointSite *bp_site)
 {
     // This isn't needed if the z/Z packets are supported in the GDB remote