From NetBSD:
Force proper LDFLAGS for MODULE, as cmake doesn't set rpath for these
Index: pcb_calculator/CMakeLists.txt
--- pcb_calculator/CMakeLists.txt.orig
+++ pcb_calculator/CMakeLists.txt
@@ -128,6 +128,9 @@ target_link_options( pcb_calculator_kiface PRIVATE
     $<$<BOOL:${KICAD_MAKE_LINK_MAPS}>:-Wl,--cref,-Map=_pcb_calculator.kiface.map>
     )
 
+set_property(TARGET pcb_calculator_kiface APPEND_STRING
+      PROPERTY LINK_FLAGS " $ENV{LDFLAGS}")
+
 # if building pcb_calculator, then also build pcb_calculator_kiface if out of date.
 add_dependencies( pcb_calculator pcb_calculator_kiface )
 
