[ELF] - Detemplate GdbIndexSection.

Patch moves Sections array to
InputFile (root class for input files).

That allows to detemplate GdbIndexSection.

Differential revision: https://reviews.llvm.org/D30976

llvm-svn: 298345
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 8d4ae10..2237c53 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -428,7 +428,7 @@
   Add(In<ELFT>::IgotPlt);
 
   if (Config->GdbIndex) {
-    In<ELFT>::GdbIndex = make<GdbIndexSection<ELFT>>();
+    In<ELFT>::GdbIndex = make<GdbIndexSection>();
     Add(In<ELFT>::GdbIndex);
   }