[ELF] - Fix cref.s test case.

[grimar]

Summary

It seems to me that the intention of -gc-sections flag was to check
that discarded is not in the output. And if so it should be
specified in the executable command line invocation and
also, the symbol must be global as local symbols are anyways
not printed.

[• espindola]

LGTM

test/ELF/cref.s

 // REQUIRES: x86
 
 // RUN: echo '.global foo; foo:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t1.o
 // RUN: echo '.global foo, bar; bar:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t2.o
 // RUN: echo '.global zed; zed:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %ta.o
 // RUN: rm -f %t.a
 // RUN: llvm-ar rcs %t.a %ta.o
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t3.o
-// RUN: ld.lld -shared -o %t1.so %t1.o -gc-sections
-// RUN: ld.lld -o /dev/null %t1.so %t2.o %t3.o %t.a -cref | FileCheck -strict-whitespace %s
+// RUN: ld.lld -shared -o %t1.so %t1.o
+// RUN: ld.lld -o /dev/null %t1.so %t2.o %t3.o %t.a -gc-sections -cref | FileCheck -strict-whitespace %s
 
 //      CHECK: Symbol                                            File
 // CHECK-NEXT: bar                                               {{.*}}2.o
 // CHECK-NEXT:                                                   {{.*}}3.o
 // CHECK-NEXT: foo                                               {{.*}}1.so
 // CHECK-NEXT:                                                   {{.*}}2.o
 // CHECK-NEXT:                                                   {{.*}}3.o
 // CHECK-NEXT: _start                                            {{.*}}3.o
 // CHECK-NEXT: baz                                               {{.*}}3.o
 // CHECK-NEXT: zed                                               {{.*}}.a({{.*}}a.o)
 // CHECK-NEXT:                                                   {{.*}}3.o
+// CHECK-NOT:  discarded
 
-.global _start, foo, bar, baz
+.global _start, foo, bar, baz, discarded
 _start:
   call foo
   call bar
   call zed
 localsym:
 baz:
 
 .section .text.a,"ax",@progbits
 discarded: