Fix broken RPATH [Linux]

Due to recent changes, the RPATH was incorrectly set to, e.g.,
`$$ORIGIN/../lib`, with an extra `$` -- the correct RPATH being `$ORIGIN/../lib`.

App/CMakeLists.txt

@@ -64,8 +64,8 @@ endif()
 #   See our deployment paper (Nejati et al 2024) for explanation.
 
 if(LINUX)
-    target_link_options(${executable_name} PRIVATE
-        "-Wl,--disable-new-dtags,-rpath,\$ORIGIN/../lib")
+    set(link_flags "-Wl,-rpath,\$ORIGIN/../lib")
+    set_target_properties(${executable_name} PROPERTIES LINK_FLAGS ${link_flags})
 elseif(APPLE)
     set(MACOSX_BUNDLE_IDENTIFIER org.bornagainproject.BornAgain)
     configure_file(${CONFIGURABLES_DIR}/MacOSXBundleInfo.plist.in ${BUILD_VAR_DIR}/Info.plist @ONLY)

GUI/CMakeLists.txt

@@ -31,6 +31,11 @@ set(BornAgain_LIBRARIES "$CACHE{BornAgain_LIBRARIES};${lib_dir}/${libprefix}${li
 # switch OFF Qt debug output in any configuration except DEBUG
 target_compile_definitions(${lib} PUBLIC $<$<NOT:$<CONFIG:Debug>>:QT_NO_DEBUG_OUTPUT>)
 
+if(LINUX)
+    set(link_flags "-Wl,-rpath,\$ORIGIN")
+    set_target_properties(${lib} PROPERTIES LINK_FLAGS ${link_flags})
+endif(LINUX)
+
 if(BORNAGAIN_PYTHON)
     target_compile_definitions(${lib} PRIVATE -DBORNAGAIN_PYTHON)
 endif()

cmake/BornAgain/MakeLib.cmake

@@ -68,8 +68,8 @@ function(MakeLib lib swigtmpdir source_files include_files)
     # Set runtime-location of library dependencies
     # See our deployment paper (Nejati et al 2024) for explanation.
     if(LINUX)
-        target_link_options(${lib} PRIVATE
-           "-Wl,--disable-new-dtags,-rpath,\$ORIGIN:\$ORIGIN/extra")
+        set(link_flags "-Wl,--disable-new-dtags,-rpath,\$ORIGIN:\$ORIGIN/../extra")
+        set_target_properties(${lib} PROPERTIES LINK_FLAGS ${link_flags})
     elseif(APPLE)
         target_link_options(${lib} PRIVATE
             "-Wl,-rpath,@loader_path,-rpath,@loader_path/extra")