Use DYLD_LIBRARY_PATH to ensure the just-built library is picked up. Make sure
to exclude the prefix however to avoid conflicts (eg. OpenGL and libGL).
--- giscanner/ccompiler.py.orig
+++ giscanner/ccompiler.py
@@ -184,7 +184,7 @@
         if os.name == 'nt':
             runtime_path_envvar = ['LIB', 'PATH']
         else:
-            runtime_path_envvar = ['LD_LIBRARY_PATH', 'DYLD_FALLBACK_LIBRARY_PATH'] if not lib_dirs_envvar else [lib_dirs_envvar]
+            runtime_path_envvar = ['LD_LIBRARY_PATH', 'DYLD_LIBRARY_PATH'] if not lib_dirs_envvar else [lib_dirs_envvar]
             # Search the current directory first
             # (This flag is not supported nor needed for Visual C++)
             args.append('-L.')
@@ -250,7 +249,8 @@
                     else:
                         args.append('-Wl,-rpath,' + library_path)
 
-            runtime_paths.append(library_path)
+            if library_path != '@MP_LIB@':
+                runtime_paths.append(library_path)
 
         for library in libraries + extra_libraries:
             if self.check_is_msvc():