llvm-dwarfdump: automatically dump both regular and .dwo variant of sections

Since users typically don't really care about the .dwo / non.dwo
distinction, this patch makes it so dwarfdump --debug-<info,...> dumps
.debug_info and (if available) also .debug_info.dwo. This simplifies
the command line interface (I've removed all dwo-specific dump
options) and makes the tool friendlier to use.

Differential Revision: https://reviews.llvm.org/D37771

llvm-svn: 313207
diff --git a/llvm/test/DebugInfo/X86/split-dwarf-omit-empty.ll b/llvm/test/DebugInfo/X86/split-dwarf-omit-empty.ll
index 4e8debb..1ce6d1c 100644
--- a/llvm/test/DebugInfo/X86/split-dwarf-omit-empty.ll
+++ b/llvm/test/DebugInfo/X86/split-dwarf-omit-empty.ll
@@ -15,8 +15,10 @@
 ; will be emitted. This emulates something more like the available_externally
 ; import performed by ThinLTO.
 
+; CHECK: .debug_info contents:
 ; CHECK: Compile Unit
 ; CHECK-NOT: Compile Unit
+; CHECK: .debug_info.dwo contents:
 
 target triple = "x86_64-pc-linux"