[Test] Make permission reset in lock_interface more reliable

Author: xymus

test/Driver/lock_interface.swift

@@ -10,21 +10,21 @@
 // RUN: echo 'import Foo' > %t/file-01.swift
 // RUN: echo 'import Foo' > %t/file-02.swift
 // RUN: echo 'import Foo' > %t/file-03.swift
-// RUN: %target-swiftc_driver -j20 %t/main.swift %t/file-01.swift %t/file-02.swift %t/file-03.swift -I %t/sdk -Xfrontend -Rmodule-interface-rebuild -module-cache-path %t/module-cache &> %t/result.txt
-// RUN: %FileCheck %s  -check-prefix=CHECK-REBUILD < %t/result.txt
+// RUN: %target-swiftc_driver -j20 %t/main.swift %t/file-01.swift %t/file-02.swift %t/file-03.swift -I %t/sdk -Xfrontend -Rmodule-interface-rebuild -module-cache-path %t/module-cache &> %t/result-with-lock.txt
 
 /// Checking that the compiler rebuilds the same module more than once can
 /// fail depending on how fast the jobs are executed. Just make sure the
 /// compiler accepts the -disable-interface-lock flag.
-// RUN: %target-swiftc_driver -j20 %t/main.swift %t/file-01.swift %t/file-02.swift %t/file-03.swift -I %t/sdk -Xfrontend -Rmodule-interface-rebuild -Xfrontend -disable-interface-lock -module-cache-path %t/module-cache-no-lock &> %t/result.txt
-// RUN: %FileCheck %s  -check-prefix=CHECK-REBUILD-NO-LOCK < %t/result.txt
+// RUN: %target-swiftc_driver -j20 %t/main.swift %t/file-01.swift %t/file-02.swift %t/file-03.swift -I %t/sdk -Xfrontend -Rmodule-interface-rebuild -Xfrontend -disable-interface-lock -module-cache-path %t/module-cache-no-lock &> %t/result-no-lock.txt
 
-// Reset the permissions
+/// Reset the permissions before running the tests likely to fail.
 // RUN: chmod a+w %t/sdk
 
 // Ensure we only build Foo module once from the interface
+// RUN: %FileCheck %s  -check-prefix=CHECK-REBUILD < %t/result-with-lock.txt
 // CHECK-REBUILD: rebuilding module 'Foo' from interface
 // CHECK-REBUILD-NOT: rebuilding module 'Foo' from interface
 // CHECK-REBUILD-NOT: building module interface without lock file
 
+// RUN: %FileCheck %s  -check-prefix=CHECK-REBUILD-NO-LOCK < %t/result-no-lock.txt
 // CHECK-REBUILD-NO-LOCK: rebuilding module 'Foo' from interface