Add test model, shore up 'build' command more

test-projects/single-sync-point/roblox-project.json

@@ -1,5 +1,5 @@
 {
-  "name": "empty",
+  "name": "single-sync-point",
   "tree": {
     "$className": "DataModel",
     "ReplicatedStorage": {

test-projects/test-model/roblox-project.json

@@ -0,0 +1,9 @@
+{
+  "name": "empty",
+  "tree": {
+    "$className": "Folder",
+    "Library": {
+      "$path": "src"
+    }
+  }
+}

test-projects/test-model/src/main.lua

@@ -0,0 +1,3 @@
+local other = require(script.Parent.other)
+
+print(other)

test-projects/test-model/src/other.lua

@@ -0,0 +1 @@
+return "Hello, world!"