tests: Enable EndToEnd tests, but skip in CI

The EndToEnd tests no longer deadlock under `swift test` and can
now be run on macOS and Linux.

The CI cannot currently run the end to end tests because SDK generator
cannot use the CI HTTP proxy to download packages.   This commit
allows the tests on macOS, so they can be run locally, but explictly
skips them in CI.

Fixes: #143

Docker/docker-compose.yaml

@@ -25,6 +25,8 @@ services:
 
   test:
     <<: *common
+    environment:
+      - JENKINS_URL
     command: /bin/bash -xcl "swift test $${WARN_AS_ERROR_ARG-} $${SANITIZER_ARG-} $${IMPORT_CHECK_ARG-}"
 
   # util

Tests/SwiftSDKGeneratorTests/EndToEndTests.swift

@@ -69,7 +69,6 @@ final class EndToEndTests: XCTestCase {
   // This takes a lock on `.build`, but if the tests are being run by `swift test` the outer Swift Package Manager
   // instance will already hold this lock, causing the test to deadlock.   We can work around this by giving
   // the `swift run swift-sdk-generator` instance its own scratch directory.
-  #if !os(macOS)
   func buildSDK(inDirectory packageDirectory: FilePath, scratchPath: String, withArguments runArguments: String) async throws -> String {
     let generatorOutput = try await Shell.readStdout(
       "cd \(packageDirectory) && swift run --scratch-path \"\(scratchPath)\" swift-sdk-generator \(runArguments)"
@@ -97,7 +96,9 @@ final class EndToEndTests: XCTestCase {
   }
 
   func testPackageInitExecutable() async throws {
-    throw XCTSkip("EndToEnd tests currently deadlock under `swift test`: https://github.com/swiftlang/swift-sdk-generator/issues/143")
+    if ProcessInfo.processInfo.environment.keys.contains("JENKINS_URL") {
+      throw XCTSkip("EndToEnd tests cannot currently run in CI: https://github.com/swiftlang/swift-sdk-generator/issues/145")
+    }
 
     var packageDirectory = FilePath(#filePath)
     packageDirectory.removeLastComponent()
@@ -145,7 +146,9 @@ final class EndToEndTests: XCTestCase {
   }
 
   func testRepeatedSDKBuilds() async throws {
-    throw XCTSkip("EndToEnd tests currently deadlock under `swift test`: https://github.com/swiftlang/swift-sdk-generator/issues/143")
+    if ProcessInfo.processInfo.environment.keys.contains("JENKINS_URL") {
+      throw XCTSkip("EndToEnd tests cannot currently run in CI: https://github.com/swiftlang/swift-sdk-generator/issues/145")
+    }
 
     var packageDirectory = FilePath(#filePath)
     packageDirectory.removeLastComponent()
@@ -168,5 +171,4 @@ final class EndToEndTests: XCTestCase {
       }
     }
   }
-  #endif
 }