Using find_package(Threads REQUIRED) instead of linking pthread directly (#1324)

* Linking to Threads::Threads instead of pthread directly 
* moved rt linking to slsSupportObject and only enable for linux

slsDetectorSoftware/CMakeLists.txt

@@ -28,11 +28,11 @@ target_link_libraries(slsDetectorObject
     PUBLIC
         slsProjectOptions
         slsSupportStatic
-        pthread
     PRIVATE
         slsProjectWarnings
 )
 
+
 set(DETECTOR_LIBRARY_TARGETS slsDetectorObject)
 
 
@@ -97,8 +97,7 @@ if(SLS_USE_TEXTCLIENT)
         add_executable(${val1} src/CmdApp.cpp)
 
         target_link_libraries(${val1} 
-        slsDetectorStatic
-        pthread
+            slsDetectorStatic
         )
         SET_SOURCE_FILES_PROPERTIES( src/Caller.cpp PROPERTIES COMPILE_FLAGS "-Wno-unused-variable -Wno-unused-but-set-variable")