[Testing] Improve validate_stdlib_generic_signatures.swift

Author: davezarzycki

test/Generics/validate_stdlib_generic_signatures.swift

@@ -1,10 +1,9 @@
 // Verifies that all of the generic signatures in the standard library are
 // minimal and canonical.
 
-// RUN: not %target-typecheck-verify-swift -verify-generic-signatures Swift 2> %t.log
-
-// RUN: grep -c "error:" %t.log | count 1
-// RUN: %FileCheck %s < %t.log
-
-// CHECK: error: unexpected error produced: generic requirement 'τ_0_0.Index : Strideable' is redundant in <τ_0_0 where τ_0_0 : RandomAccessCollection, τ_0_0.Index : Strideable, τ_0_0.Indices == Range<τ_0_0.Index>, τ_0_0.Index.Stride == Int>
+// RUN: not %target-typecheck-verify-swift -verify-generic-signatures Swift 2>&1 | %FileCheck %s
 
+// CHECK-NOT: error:
+// CHECK-DAG: error: unexpected error produced: generic requirement 'τ_0_0.Index : Strideable' is redundant in <τ_0_0 where τ_0_0 : RandomAccessCollection, τ_0_0.Index : Strideable, τ_0_0.Indices == Range<τ_0_0.Index>, τ_0_0.Index.Stride == Int>
+// CHECK-DAG: error: diagnostic produced elsewhere: generic requirement 'τ_0_0.Index : Strideable' is redundant in <τ_0_0 where τ_0_0 : RandomAccessCollection, τ_0_0.Index : Strideable, τ_0_0.Indices == Range<τ_0_0.Index>, τ_0_0.Index.Stride == Int>
+// CHECK-NOT: error: