[clang] - Simplify tools::SplitDebugName.

This is an updated version of the D54576, which was reverted.

Problem was that SplitDebugName calls the InputInfo::getFilename
which asserts if InputInfo given is not of type Filename:

const char *getFilename() const {
  assert(isFilename() && "Invalid accessor.");
  return Data.Filename;
}
At the same time at that point, it can be of type Nothing and
we need to use getBaseInput(), like original code did.

Differential revision: https://reviews.llvm.org/D55006

llvm-svn: 348352
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 34a9234..67d55f4 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -817,7 +817,7 @@
   if (Args.hasArg(options::OPT_gsplit_dwarf) &&
       getToolChain().getTriple().isOSLinux())
     SplitDebugInfo(getToolChain(), C, *this, JA, Args, Output,
-                   SplitDebugName(Args, Inputs[0], Output));
+                   SplitDebugName(Args, Output));
 }
 
 namespace {