message: Fix Package.swift compilation with Xcode 11
  Also cuts the build time with Xcode 12 from 15 seconds to 2.
diff: @@ -124,9 +124,9 @@ let package = Package(
  name: "SyncClient",
  dependencies: ["Storage"],
  path: "src",
  - exclude: [
  + exclude: ([
  "realm/sync/crypto_server_openssl.cpp",
  - ] + syncCommandSources + syncServerSources,
  + ] + syncCommandSources + syncServerSources) as [String],
  sources: [
  "realm/sync",
  "realm/util/network.cpp",
  @@ -146,9 +146,9 @@ let package = Package(
  name: "SyncServer",
  dependencies: ["SyncClient"],
  path: "src",
  - exclude: [
  + exclude: ([
  "realm/sync/crypto_server_openssl.cpp",
  - ] + syncCommandSources,
  + ] + syncCommandSources) as [String],
  sources: syncServerSources,
  publicHeadersPath: "realm/sync/impl", // hack
  cxxSettings: cxxSettings,
  @@ -166,11 +166,11 @@ let package = Package(
  ],
  sources: ["realm/object-store"],
  publicHeadersPath: "realm/object-store",
  - cxxSettings: [
  + cxxSettings: ([
  .define("REALM_ENABLE_SYNC", to: "1"),
  .define("REALM_PLATFORM_APPLE", to: "1", .when(platforms: [.macOS, .iOS, .tvOS, .watchOS])),
  .headerSearchPath("realm/object-store")
  - ] + cxxSettings),
  + ] + cxxSettings) as [CXXSetting]),
  .target(
  name: "ObjectStoreTests",
  dependencies: ["ObjectStore", "SyncServer"],
  @@ -179,12 +179,12 @@ let package = Package(
  "benchmarks",
  "notifications-fuzzer"
  ],
  - cxxSettings: [
  + cxxSettings: ([
  .define("REALM_ENABLE_SYNC", to: "1"),
  .define("REALM_PLATFORM_APPLE", to: "1", .when(platforms: [.macOS, .iOS, .tvOS, .watchOS])),
  .headerSearchPath("."),
  .headerSearchPath("../../external/catch/single_include")
  - ] + cxxSettings)
  + ] + cxxSettings) as [CXXSetting])
  ],
  cxxLanguageStandard: .cxx1z
  )
  