Fix release build.

Move Prototypes to a test target so that it's not built under the release configuration. Disable the PEG prototype in Exercises since it depends on Prototypes.

Resolves #288.

Author: rxwei

Package.swift

@@ -76,7 +76,7 @@ let package = Package(
                 .unsafeFlags(["-Xfrontend", "-enable-experimental-pairwise-build-block"]),
                 .unsafeFlags(["-Xfrontend", "-disable-availability-checking"])
             ]),
-        .target(
+        .testTarget(
             name: "Prototypes",
             dependencies: ["_RegexParser", "_StringProcessing"],
             swiftSettings: [
@@ -100,7 +100,7 @@ let package = Package(
         // MARK: Exercises
         .target(
             name: "Exercises",
-            dependencies: ["_RegexParser", "Prototypes", "_StringProcessing", "RegexBuilder"],
+            dependencies: ["_RegexParser", "_StringProcessing", "RegexBuilder"],
             swiftSettings: [
                 .unsafeFlags(["-Xfrontend", "-enable-experimental-pairwise-build-block"]),
                 .unsafeFlags(["-Xfrontend", "-disable-availability-checking"])

Sources/Exercises/Exercises.swift

@@ -16,7 +16,6 @@ public enum Exercises {
       HandWrittenParticipant.self,
       RegexDSLParticipant.self,
       RegexLiteralParticipant.self,
-      PEGParticipant.self,
       NSREParticipant.self,
     ]
   }

Sources/Exercises/Participants/PEGParticipant.swift

@@ -9,6 +9,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+// Disabled because Prototypes is a test target.
+#if false
+
 struct PEGParticipant: Participant {
   static var name: String { "PEG" }
 }
@@ -51,3 +54,4 @@ private func graphemeBreakPropertyData(forLine line: String) -> GraphemeBreakEnt
 
 }
 
+#endif