[test] Fix swiftpm tests that relied on minimum deployment target

We don't want to test the specific version, only that it's getting
formed correctly into arguments, so use the oldest supported version
from swiftpm's perspective.

rdar://76191577

Author: benlangmuir

Tests/SKSwiftPMWorkspaceTests/SwiftPMWorkspaceTests.swift

@@ -15,6 +15,7 @@ import SPMBuildCore
 #endif
 import Build
 import LanguageServerProtocol
+import PackageModel
 import SKCore
 import SKSwiftPMWorkspace
 import SKTestSupport
@@ -83,8 +84,6 @@ final class SwiftPMWorkspaceTests: XCTestCase {
   }
 
   func testBasicSwiftArgs() throws {
-    throw XCTSkip("rdar://76191577");
-
     // FIXME: should be possible to use InMemoryFileSystem.
     let fs = localFileSystem
     try! withTemporaryDirectory(removeTreeOnDeinit: true) { tempDir in
@@ -120,7 +119,8 @@ final class SwiftPMWorkspaceTests: XCTestCase {
 
       check("-target", arguments: arguments) // Only one!
   #if os(macOS)
-      check("-target", hostTriple.tripleString(forPlatformVersion: "10.10"), arguments: arguments)
+      let versionString = PackageModel.Platform.macOS.oldestSupportedVersion.versionString
+      check("-target", hostTriple.tripleString(forPlatformVersion: versionString), arguments: arguments)
       check("-sdk", arguments: arguments)
       check("-F", arguments: arguments)
   #else
@@ -323,8 +323,6 @@ final class SwiftPMWorkspaceTests: XCTestCase {
   }
 
   func testBasicCXXArgs() throws {
-    throw XCTSkip("rdar://76191577");
-
     // FIXME: should be possible to use InMemoryFileSystem.
     let fs = localFileSystem
     try! withTemporaryDirectory(removeTreeOnDeinit: true) { tempDir in
@@ -362,8 +360,9 @@ final class SwiftPMWorkspaceTests: XCTestCase {
         checkNot("-arch", arguments: arguments)
         check("-target", arguments: arguments) // Only one!
     #if os(macOS)
+        let versionString = PackageModel.Platform.macOS.oldestSupportedVersion.versionString
         check("-target",
-          hostTriple.tripleString(forPlatformVersion: "10.10"), arguments: arguments)
+          hostTriple.tripleString(forPlatformVersion: versionString), arguments: arguments)
         check("-isysroot", arguments: arguments)
         check("-F", arguments: arguments)
     #else