[flang] Fix ppc64le-flang-rhel-test buildbot failure (#142269)

PR#142073 introduced a new test that checks the
prefer-vector-width function attribute. This test was not accounting for
target triples that include default function attributes.

This patch updates prefer-vector-width.f90 to ignore extra function
attributes.

---------

Co-authored-by: Cameron McInally <[email protected]>

Author: mcinally

flang/test/Driver/prefer-vector-width.f90

@@ -1,16 +1,18 @@
 ! Test that -mprefer-vector-width works as expected.
 
 ! RUN: %flang_fc1 -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-DEF
-! RUN: %flang_fc1 -mprefer-vector-width=none -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-NONE
-! RUN: %flang_fc1 -mprefer-vector-width=128 -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-128
-! RUN: %flang_fc1 -mprefer-vector-width=256 -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-256
-! RUN: not %flang_fc1 -mprefer-vector-width=xxx  -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-INVALID
+! RUN: %flang_fc1 -mprefer-vector-width=none -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefixes=CHECK,CHECK-NONE
+! RUN: %flang_fc1 -mprefer-vector-width=128 -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefixes=CHECK,CHECK-128
+! RUN: %flang_fc1 -mprefer-vector-width=256 -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefixes=CHECK,CHECK-256
+! RUN: not %flang_fc1 -mprefer-vector-width=xxx  -emit-llvm -o - %s 2>&1| FileCheck %s --check-prefixes=CHECK-INVALID
 
 subroutine func
 end subroutine func
 
-! CHECK-DEF-NOT: attributes #0 = { "prefer-vector-width"={{.*}}
-! CHECK-NONE: attributes #0 = { "prefer-vector-width"="none"
-! CHECK-128: attributes #0 = { "prefer-vector-width"="128"
-! CHECK-256: attributes #0 = { "prefer-vector-width"="256"
-! CHECK-INVALID:error: invalid value 'xxx' in '-mprefer-vector-width=xxx'
+! CHECK: define {{.+}} @func{{.*}} #[[ATTRS:[0-9]+]]
+! CHECK: attributes #[[ATTRS]] =
+! CHECK-DEF-NOT: "prefer-vector-width"
+! CHECK-NONE-SAME: "prefer-vector-width"="none"
+! CHECK-128-SAME: "prefer-vector-width"="128"
+! CHECK-256-SAME: "prefer-vector-width"="256"
+! CHECK-INVALID: error: invalid value 'xxx' in '-mprefer-vector-width=xxx'