Add missing code for parser entry template and fix build-script.py (#1352)

Author: kimdv

CodeGeneration/Sources/generate-swiftsyntax/templates/swiftparser/ParserEntryFile.swift

@@ -87,7 +87,15 @@ let parserEntryFile = SourceFileSyntax(leadingTrivia: generateCopyrightHeader(fo
           return into
         }
 
-        let unexpected = RawUnexpectedNodesSyntax(elements: remainingTokens, arena: self.arena)
+        let existingUnexpected: [RawSyntax]
+        if let unexpectedNode = layout.children[layout.children.count - 1] {
+           assert(unexpectedNode.is(RawUnexpectedNodesSyntax.self))
+           existingUnexpected = unexpectedNode.as(RawUnexpectedNodesSyntax.self).elements
+        } else {
+           existingUnexpected = []
+        }
+        let unexpected = RawUnexpectedNodesSyntax(elements: existingUnexpected + remainingTokens, arena: self.arena)
+
         let withUnexpected = layout.replacingChild(at: layout.children.count - 1, with: unexpected.raw, arena: self.arena)
         return R.init(withUnexpected)!
       }

build-script.py

@@ -433,8 +433,8 @@ def verify_gyb_generated_files(gyb_exec: str, verbose: bool) -> None:
 def verify_code_generated_files(
     toolchain: str, verbose: bool
 ) -> None:
-    
-    
+    self_temp_dir = tempfile.mkdtemp()
+
     try:
         run_code_generation(
             source_dir=self_temp_dir,
@@ -451,7 +451,7 @@ def verify_code_generated_files(
 
     for module in ["SwiftBasicFormat", "IDEUtils", \
       "SwiftParser", "SwiftSyntax", "SwiftSyntaxBuilder"]:
-      self_generated_dir = os.path.join(self_temp_dir, "Sources", module, "generated")
+      self_generated_dir = os.path.join(self_temp_dir, module, "generated")
       user_generated_dir = os.path.join(SOURCES_DIR, module, "generated")
       check_generated_files_match(self_generated_dir, user_generated_dir)