[llvm-objdump] - Improve the error message for "removing a section that is used by relocation" case.

[grimar]

Summary

This refines/improves the error message introduced in D58625

[jhenderson]

The message rubs me the wrong way slightly (not mentioning where the relocation itself is), but I think the information is probably sufficient, and I don't have any better suggestions, so LGTM. But please wait for @rupprecht too.

llvm/trunk/test/tools/llvm-objcopy/ELF/strip-section-err.test

 ## Check we cannot remove a section containing symbols
 ## referenced by relocations contained in the object.
 
 # RUN: yaml2obj %s > %t1
 # RUN: not llvm-objcopy -R .data %t1 2>&1 | FileCheck %s
-# CHECK: error: Section .data cannot be removed because of symbol 'foo' used by the relocation patching offset 0x1 from section .rela.text.
+# CHECK: error: Section .data can't be removed: (.text+0x1) has relocation against symbol 'foo'
 
 ## Check the behavior when we also remove the relocation section.
 ## We have no reference in this case and hence no error should be emitted.
 
 # RUN: yaml2obj %s > %t2
 # RUN: llvm-objcopy -R .data -R .rela.text %t2 %t3
 # RUN: llvm-objdump --section-headers %t3 | FileCheck %s --check-prefix=NOSEC
 # NOSEC-NOT: .data

llvm/trunk/tools/llvm-objcopy/ELF/Object.cpp

if (ToRemove(Symbols))
     return createStringError(llvm::errc::invalid_argument,
                              "Symbol table %s cannot be removed because it is "
                              "referenced by the relocation section %s.",
                              Symbols->Name.data(), this->Name.data());
 
   for (const Relocation &R : Relocations) {
     if (!R.RelocSymbol->DefinedIn || !ToRemove(R.RelocSymbol->DefinedIn))
       continue;
-    return createStringError(
-        llvm::errc::invalid_argument,
-        "Section %s cannot be removed because of symbol '%s' "
-        "used by the relocation patching offset 0x%" PRIx64 " from section %s.",
-        R.RelocSymbol->DefinedIn->Name.data(), R.RelocSymbol->Name.c_str(),
-        R.Offset, this->Name.data());
+    return createStringError(llvm::errc::invalid_argument,
+                             "Section %s can't be removed: (%s+0x%" PRIx64
+                             ") has relocation against symbol '%s'",
+                             R.RelocSymbol->DefinedIn->Name.data(),
+                             SecToApplyRel->Name.data(), R.Offset,
+                             R.RelocSymbol->Name.c_str());
   }
 
   return Error::success();
 }
 
 template <class SymTabType>
 void RelocSectionWithSymtabBase<SymTabType>::initialize(
     SectionTableRef SecTable) {