skip a couple of tests when running in an environment that does not support changing the working directory (#6310)

motivation: stable ci

changes: skip a couple of new tests that are sensitive to env where we cannot change the working directory

Author: tomerd

Tests/CommandsTests/PackageRegistryToolTests.swift

@@ -417,6 +417,13 @@ final class PackageRegistryToolTests: CommandsTestCase {
     }
 
     func testPublishingUnsignedPackage() throws {
+        #if os(Linux)
+        // needed for archiving
+        guard SPM_posix_spawn_file_actions_addchdir_np_supported() else {
+            throw XCTSkip("working directory not supported on this platform")
+        }
+        #endif
+
         let packageIdentity = "test.my-package"
         let version = "0.1.0"
         let registryURL = "https://packages.example.com"
@@ -589,6 +596,13 @@ final class PackageRegistryToolTests: CommandsTestCase {
             "skipping because test environment doesn't support concurrency"
         )
 
+        #if os(Linux)
+        // needed for archiving
+        guard SPM_posix_spawn_file_actions_addchdir_np_supported() else {
+            throw XCTSkip("working directory not supported on this platform")
+        }
+        #endif
+
         let observabilityScope = ObservabilitySystem.makeForTesting().topScope
 
         let packageIdentity = "test.my-package"