Use explicit dependencies for FileCheck and cllvm

Author: Harlan

Package.swift

@@ -10,8 +10,8 @@ let package = Package(
       targets: ["LLVM"]),
   ],
   dependencies: [
-    .package(url: "https://github.com/trill-lang/cllvm.git", .branch("master")),
-    .package(url: "https://github.com/trill-lang/FileCheck.git", .branch("master")),
+    .package(url: "https://github.com/trill-lang/cllvm.git", from: "0.0.3"),
+    .package(url: "https://github.com/trill-lang/FileCheck.git", from: "0.0.3"),
   ],
   targets: [
     .target(