Load source file of the hier_block explicitly (#2559)

* Add a test to make sure that lib modules (loaded via -y option) can be a hier_block.

* Add HDL file of the hier_block to the source list if the module is loaded via -y option.

(Each hier_block is treated as a top module when processing the hier_block.)

* Use "\n" for delimiter as the other files

src/V3EmitCMake.cpp

@@ -229,6 +229,8 @@ class CMakeEmitter {
                     *of << deslash(" ${CMAKE_CURRENT_BINARY_DIR}/" + (*child)->hierWrapper(true));
                 }
                 *of << " ";
+                const string vFile = hblockp->vFileIfNecessary();
+                if (!vFile.empty()) *of << vFile << " ";
                 const V3StringList& vFiles = v3Global.opt.vFiles();
                 for (const string& i : vFiles) *of << V3Os::filenameRealPath(i);
                 *of << " VERILATOR_ARGS ";