Add "xfail" entries

Author: groue

projects.json

@@ -1015,10 +1015,24 @@
         "action": "BuildSwiftPackage",
         "build_tests": "true",
         "configuration": "release",
-        "tags": "sourcekit-disabled swiftpm"
+        "tags": "sourcekit-disabled swiftpm",
+        "xfail": [
+            {
+                "issue": "https://github.com/swiftlang/swift/issues/78635",
+                "compatibility": "6.1",
+                "branch": ["main"],
+            }
+        ]
       },
       {
-        "action": "TestSwiftPackage"
+        "action": "TestSwiftPackage",
+        "xfail": [
+            {
+                "issue": "https://github.com/swiftlang/swift/issues/78635",
+                "compatibility": "6.1",
+                "branch": ["main"],
+            }
+        ]
       }
     ]
   },