Update PKG_LIBS if TBB_LIB is defined

Author: hsbadr

src/Makevars.in

@@ -8,7 +8,7 @@ PKG_CPPFLAGS = -I../inst/include
 endif
 
 ifdef TBB_LIB
-PKG_LIBS = -L$(TBB_LIB) -ltbb
+PKG_LIBS = -Wl,-L,"$(TBB_LIB)" -Wl,-rpath,"$(TBB_LIB)" -ltbb -ltbbmalloc
 endif
 
 ifeq ($(OS), Windows_NT)