Debug Info: Use the major runtime version only to populate the

DW_AT_APPLE_major_runtime_vers attribute.

LLDB currently doesn't use this field, so this discontinuity is still safe.
Because of the dependency on the version number this is hard to write a
testcase for.

rdar://problem/24176158

Author: adrian-prantl

lib/IRGen/IRGenDebugInfo.cpp

@@ -128,15 +128,15 @@ IRGenDebugInfo::IRGenDebugInfo(const IRGenOptions &Opts,
   StringRef Flags = Opts.DWARFDebugFlags;
   unsigned Major, Minor;
   std::tie(Major, Minor) = version::getSwiftNumericVersion();
-  unsigned RuntimeVersion = Major*100 + Minor;
+  unsigned MajorRuntimeVersion = Major;
 
   // No split DWARF on Darwin.
   StringRef SplitName = StringRef();
   // Note that File + Dir need not result in a valid path.
   // Clang is doing the same thing here.
   TheCU = DBuilder.createCompileUnit(
       Lang, AbsMainFile, Opts.DebugCompilationDir, Producer, IsOptimized,
-      Flags, RuntimeVersion, SplitName,
+      Flags, MajorRuntimeVersion, SplitName,
       Opts.DebugInfoKind == IRGenDebugInfoKind::LineTables
           ? llvm::DIBuilder::LineTablesOnly
           : llvm::DIBuilder::FullDebug);