Add comments.

llvm-svn: 281098
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index fbe34e6..73bb65d 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -478,6 +478,10 @@
   }
 
   this->initStringTable();
+
+  // DSOs are identified by soname, and they usually contain
+  // DT_SONAME tag in their header. But if they are missing,
+  // filenames are used as default sonames.
   SoName = sys::path::filename(this->getName());
 
   if (!DynamicSec)