CONFIG: reinstate FOAM_LD_LIBRARY_PATH adjustments (#2801)

- the special MacOS dlopen handling (commit f584ec97d0)
  did not fully solve the problem with SIP clearing.

  Eg, sourcing the RunFunctions (for runParallel) triggers SIP and
  clears DYLD_LIBRARY_PATH. With the cleared path it finds the dummy
  libraries: the dummy Pstream::init() fails.

bin/foamJob

@@ -23,6 +23,13 @@
 # If dispatching via foamExec
 foamExec="$WM_PROJECT_DIR/bin/tools/foamExec"
 
+# Darwin workaround - SIP clearing DYLD_LIBRARY_PATH variable
+if [ -n "$FOAM_LD_LIBRARY_PATH" ] && [ -z "$DYLD_LIBRARY_PATH" ]
+then
+    export DYLD_LIBRARY_PATH="$FOAM_LD_LIBRARY_PATH"
+fi
+
+
 #------------------------------------------------------------------------------
 
 usage() {