Fix/matterhorn compilation on clang (#1584)

* dont use this

* moved explicit instantiation after definiting templated functions

slsDetectorServers/matterhornServer/src/BaseMatterhornServerImpl.hpp

@@ -21,6 +21,8 @@ class BaseMatterhornServerImpl
     : public DetectorServerImpl<
           is_stop_server<DerivedMatterhornServerImpl>::value> {
   public:
+    using BaseServerImpl =
+        DetectorServerImpl<is_stop_server<DerivedMatterhornServerImpl>::value>;
     BaseMatterhornServerImpl();
     ~BaseMatterhornServerImpl() = default;
 
@@ -93,7 +95,7 @@ void BaseMatterhornServerImpl<DerivedMatterhornServerImpl>::setupDetector() {
     // TODO: extend
     try {
         // stop server does not talk to the board
-        if constexpr (!this->stop_server) {
+        if constexpr (!BaseServerImpl::stop_server) {
             set_num_frames(1);
             set_num_triggers(1);
             set_counter_mask(0xF); // enable counter all counters by default

slsDetectorServers/slsDetectorServer_cpp/src/DetectorServerImpl.cpp

@@ -5,9 +5,6 @@
 
 namespace sls {
 
-template class DetectorServerImpl<true>;  // forward declare
-template class DetectorServerImpl<false>; // forward declare
-
 template <bool isStopServer>
 DetectorServerImpl<isStopServer>::DetectorServerImpl() {
     udpDetails[0].srcport = DEFAULT_UDP_SRC_PORTNO;
@@ -114,4 +111,9 @@ DetectorServerImpl<isStopServer>::get_detector_setup_status() const {
     return detectorSetupStatus;
 }
 
+template class DetectorServerImpl<true>;  // explicit instantiation for stop
+                                          // server
+template class DetectorServerImpl<false>; // explicit instantiation for control
+                                          // server
+
 } // namespace sls