Only test debug build configuration on Windows

With the recent changes to the automated test, which augmented the Tests
to run against the Native and Swift Build build system, in addition to
the debug and release build configuraiton, and with `swift test` buffer
the output on Windows (#8928), the theory is the Windows self hosted
pipeline is failing due to the number of automated test, which causes
Jenkins to hit the "Build Timeout" algorithim, causing Jenkins to abort
the build as there is no output to the console.

I norer to unblock development, a change was made to run test against
the Debug build configuration on Windows until a proper solution is
availabe.

Related to #9159
Issue: rdar://160936699

Author: bkhouri

Sources/_InternalTestSupport/BuildSystemProvider+Supported.swift

@@ -12,6 +12,8 @@
 
 import struct SPMBuildCore.BuildSystemProvider
 import enum PackageModel.BuildConfiguration
+import struct Basics.Environment
+import struct Basics.EnvironmentKey
 
 public var SupportedBuildSystemOnAllPlatforms: [BuildSystemProvider.Kind] = BuildSystemProvider.Kind.allCases.filter { $0 != .xcode }
 
@@ -28,10 +30,29 @@ public struct BuildData {
     public let config: BuildConfiguration
 }
 
+package let TEST_ONLY_DEBUG_ENV_VAR = EnvironmentKey("SWIFTPM_TEST_ONLY_DEBUG_BUILD_CONFIGURATION")
 public func getBuildData(for buildSystems: [BuildSystemProvider.Kind]) -> [BuildData] {
-    buildSystems.flatMap { buildSystem in
-        BuildConfiguration.allCases.compactMap { config in
+    let buildConfigurations: [BuildConfiguration]
+    if let value = Environment.current[TEST_ONLY_DEBUG_ENV_VAR], value.isTruthy {
+        buildConfigurations = [.debug]
+    } else {
+        buildConfigurations = BuildConfiguration.allCases
+    }
+    return buildSystems.flatMap { buildSystem in
+        buildConfigurations.compactMap { config in
             return BuildData(buildSystem: buildSystem, config: config)
         }
     }
 }
+
+
+extension String {
+    package var isTruthy: Bool {
+        switch self.lowercased() {
+        case "true", "1", "yes":
+            return true
+        default:
+            return false
+        }
+    }
+}

Tests/_InternalTestSupportTests/BuildSystemProviderSupportedTests.swift

@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2024-2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import _InternalTestSupport
+import Testing
+import struct SPMBuildCore.BuildSystemProvider
+import enum PackageModel.BuildConfiguration
+import struct Basics.Environment
+
+@Suite(
+    .tags(
+        .TestSize.small,
+    )
+)
+struct BuildSystemProviderSupportedTests {
+
+    @Test(
+        .serialized,
+        arguments: [
+            [BuildSystemProvider.Kind.native],
+            [BuildSystemProvider.Kind.native, .xcode],
+            [BuildSystemProvider.Kind.native, .xcode, .swiftbuild],
+        ], [true, false],
+    )
+    func getBuildDataReturnsExpectedTests(
+        buildSystemsUT: [BuildSystemProvider.Kind],
+        setEnvironmantVariable: Bool,
+    ) async throws {
+        let expectedCount: Int
+        let customEnv: Environment
+
+        if setEnvironmantVariable {
+            expectedCount = buildSystemsUT.count
+            customEnv = [TEST_ONLY_DEBUG_ENV_VAR : "true"]
+        } else {
+            expectedCount = buildSystemsUT.count * BuildConfiguration.allCases.count
+            customEnv = [:]
+        }
+
+        try Environment.makeCustom(customEnv) {
+            let actual = getBuildData(for: buildSystemsUT)
+
+            #expect(actual.count == expectedCount)
+        }
+
+    }
+}

Tests/_InternalTestSupportTests/String+ExtensionTests.swift

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2024-2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import _InternalTestSupport
+import Testing
+
+@Suite(
+    .tags(
+        .TestSize.small,
+    )
+)
+struct StringExtensionTests {
+
+    @Test(
+        arguments: [
+            (value: "", expected: false),
+            (value: " ", expected: false),
+            (value: "0", expected: false),
+            (value: "1", expected: true),
+            (value: "true", expected: true),
+            (value: "True", expected: true),
+            (value: "TrUe", expected: true),
+            (value: "ftrue", expected: false),
+            (value: "truef", expected: false),
+            (value: "ftruef", expected: false),
+            (value: "YES", expected: true),
+            (value: "YEs", expected: true),
+            (value: "yEs", expected: true),
+            (value: "yes", expected: true),
+            (value: "fyes", expected: false),
+            (value: "yesf", expected: false),
+            (value: "fyesf", expected: false),
+            (value: "11", expected: false),
+        ],
+    )
+    func isTruthyReturnsCorrectValue(
+        valueUT: String,
+        expected: Bool,
+    ) async throws {
+        let actual = valueUT.isTruthy
+
+        #expect(actual == expected, "Value \(valueUT) should be \(expected)")
+    }
+}

Utilities/build-using-self

@@ -136,6 +136,10 @@ def is_on_darwin() -> bool:
     return platform.system() == "Darwin"
 
 
+def is_on_windows() -> bool:
+    return platform.system() == "Windows"
+
+
 def set_environment(
     *,
     swiftpm_bin_dir: pathlib.Path,
@@ -147,6 +151,10 @@ def set_environment(
         sdk_root = call_output(shlex.split("xcrun --show-sdk-path --sdk macosx"))
         logging.debug("macos sdk root = %r", sdk_root)
         os.environ["SDKROOT"] = sdk_root
+
+    if is_on_windows():
+        # GH #9159: Temprorarily set this environment until we figure out why the Windows internal CI is hanging
+        os.environ["SWIFTPM_TEST_ONLY_DEBUG_BUILD_CONFIGURATION"] = "true"
     log_environment()