Fix test and add missing return for llvm-lto2 error case

[tejohnson]

Summary

This test was missing the target triple, which was exposed by an
upcoming bugfix that requires getting the target earlier in the LTO API.

Once I fixed that, the case with the invalid character error stopped
returning 1 from llvm-lto2 and the test reported a failure. Fixed by
adding the missing return from llvm-lto2. Apparently we were failing
when we eventually tried to get the target.

[tejohnson]

Although the dependent patch is no longer needed, I still believe this is a correct fix.

[mehdi_amini]

LGTM.

But are these two changes related?

[tejohnson]

In D30585#694542, @mehdi_amini wrote:

LGTM.

But are these two changes related?

Yes, because we were only getting an (expected) error return because of the missing target.

test/tools/llvm-lto2/errors.ll

 ; RUN: llvm-as %s -o %t.bc
 ; RUN: not llvm-lto2 -o %t2.o %t.bc 2>&1 | FileCheck --check-prefix=ERR1 %s
 ; RUN: not llvm-lto2 -o %t2.o -r %t.bc,foo,p -r %t.bc,bar,p %t.bc 2>&1 | FileCheck --check-prefix=ERR2 %s
 ; RUN: not llvm-lto2 -o %t2.o -r %t.bc,foo,q %t.bc 2>&1 | FileCheck --check-prefix=ERR3 %s
 ; RUN: not llvm-lto2 -o %t2.o -r foo %t.bc 2>&1 | FileCheck --check-prefix=ERR4 %s
 
 ; ERR1: missing symbol resolution for {{.*}}.bc,foo
 ; ERR2: unused symbol resolution for {{.*}}.bc,bar
 ; ERR3: invalid character q in resolution: {{.*}}.bc,foo
 ; ERR4: invalid resolution: foo
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
 
 @foo = global i32 0

tools/llvm-lto2/llvm-lto2.cpp

for (std::string R : SymbolResolutions) {
     SymbolResolution Res;
     for (char C : Rest) {
       if (C == 'p')
         Res.Prevailing = true;
       else if (C == 'l')
         Res.FinalDefinitionInLinkageUnit = true;
       else if (C == 'x')
         Res.VisibleToRegularObj = true;
-      else
+      else {
         llvm::errs() << "invalid character " << C << " in resolution: " << R
                      << '\n';
+        return 1;
+      }
     }
     CommandLineResolutions[{FileName, SymbolName}].push_back(Res);
   }
 
   std::vector<std::unique_ptr<MemoryBuffer>> MBs;
 
   Config Conf;
   Conf.DiagHandler = [](const DiagnosticInfo &DI) {