Prevent unhandled file build warnings. (#718)

Resolve #717 Signed-off-by: Ross Goldberg <484615+rgoldberg@users.noreply.github.com>

Author: rgoldberg

Package.swift

@@ -97,6 +97,7 @@ var package = Package(
  .testTarget(
  name: "ArgumentParserExampleTests",
  dependencies: ["ArgumentParserTestHelpers"],
+ exclude: ["Snapshots"],
  resources: [.copy("CountLinesTest.txt")]),
  .testTarget(
  name: "ArgumentParserGenerateDoccReferenceTests",

Package@swift-5.8.swift

@@ -98,6 +98,7 @@ var package = Package(
  .testTarget(
  name: "ArgumentParserExampleTests",
  dependencies: ["ArgumentParserTestHelpers"],
+ exclude: ["Snapshots"],
  resources: [.copy("CountLinesTest.txt")]),
  .testTarget(
  name: "ArgumentParserGenerateDoccReferenceTests",