Update “unable to load standard library” test (#23990)

One of the subtests of Misc/fatal_error.swift assumes that Swift.swiftmodule is located purely based on the resource directory. It can now also be located in the SDK, so the test needs to be updated. Fixes <rdar://problem/49665477>.
# Conflicts:
#	test/Misc/fatal_error.swift

Author: beccadax

test/Misc/fatal_error.swift

@@ -1,5 +1,7 @@
-// RUN: not %target-swift-frontend -typecheck %s -sdk "" 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=NO-MODULE %s
-// RUN: not %target-swift-frontend -typecheck %s -resource-dir / 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=NO-STDLIB %s
+// RUN: %empty-directory(%t)
+
+// RUN: not %target-swift-frontend -typecheck %s -sdk %t 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=NO-MODULE %s
+// RUN: not %target-swift-frontend -typecheck %s -resource-dir %t -sdk %t 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=NO-STDLIB %s
 
 // NO-MODULE: error: no such module 'NonExistent'