tests: Run tests on Linux CI

The EndToEnd tests cannot currently be run:

* they deadlock when run under `swift test` (swiftlang#143)
* the CI requires the use of an HTTP proxy to download from the
  Internet, but SDK generator does not support proxies (swiftlang#145)

The tests are not compiled on macOS, but this commit marks
them with `XCTSkip` so they are not run on Linux either.

Future commits will loosen these restrictions.

Fixes swiftlang#45

Docker/docker-compose.yaml

@@ -25,7 +25,7 @@ services:
 
   test:
     <<: *common
-    command: /bin/bash -xcl "./Utilities/test.sh $${WARN_AS_ERROR_ARG-} $${SANITIZER_ARG-} $${IMPORT_CHECK_ARG-}"
+    command: /bin/bash -xcl "swift test $${WARN_AS_ERROR_ARG-} $${SANITIZER_ARG-} $${IMPORT_CHECK_ARG-}"
 
   # util
 

Tests/SwiftSDKGeneratorTests/EndToEndTests.swift

@@ -39,6 +39,8 @@ final class EndToEndTests: XCTestCase {
 
   #if !os(macOS)
   func testPackageInitExecutable() async throws {
+    throw XCTSkip("EndToEnd tests currently deadlock under `swift test`: https://github.com/swiftlang/swift-sdk-generator/issues/143")
+
     let fm = FileManager.default
 
     var packageDirectory = FilePath(#filePath)
@@ -102,6 +104,8 @@ 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")
+
     let fm = FileManager.default
 
     var packageDirectory = FilePath(#filePath)