COMP: make the scotch librt dependency conditional

src/parallel/decompose/ptscotchDecomp/Make/options

@@ -16,4 +16,9 @@ LIB_LIBS = \
     -L$(FOAM_EXT_LIBBIN) \
     -L$(FOAM_EXT_LIBBIN)/$(FOAM_MPI) \
     -lptscotch -lptscotcherrexit \
-    -lscotch -lrt
+    -lscotch
+
+/* May require librt, but scotch does not declare the dependency */
+ifeq ("$(SO)","so")
+    LIB_LIBS += -lrt
+endif

src/parallel/decompose/scotchDecomp/Make/options

@@ -12,4 +12,9 @@ EXE_INC = \
 
 LIB_LIBS = \
     -L$(SCOTCH_LIB_DIR) \
-    -lscotch -lscotcherrexit -lrt
+    -lscotch -lscotcherrexit
+
+/* May require librt, but scotch does not declare the dependency */
+ifeq ("$(SO)","so")
+    LIB_LIBS += -lrt
+endif