Add a comment about subtracting two non abs symbols. NFC.

llvm-svn: 321458

lld/ELF/ScriptParser.cpp

@@ -151,6 +151,7 @@ static ExprValue add(ExprValue A, ExprValue B) {
 }
 
 static ExprValue sub(ExprValue A, ExprValue B) {
+  // The distance between two symbols in sections is absolute.
   if (!A.isAbsolute() && !B.isAbsolute())
     return A.getValue() - B.getValue();
   return {A.Sec, false, A.getSectionOffset() - B.getValue(), A.Loc};