[ELF] Simplify findOrphanPos. NFC

When the orphan section is placed after i, incrementing then
decreamenting is quite difficult to understand. Simplify the code to a
single loop to make the intention clearer.

Author: MaskRay

lld/ELF/Writer.cpp

@@ -950,6 +950,11 @@ findOrphanPos(SmallVectorImpl<SectionCommand *>::iterator b,
   if (!isa<OutputDesc>(*i))
     return e;
 
+  auto isOutputSecWithInputSections = [](SectionCommand *cmd) {
+    auto *osd = dyn_cast<OutputDesc>(cmd);
+    return osd && osd->osec.hasInputSections;
+  };
+
   // If i's rank is larger, the orphan section can be placed before i.
   //
   // However, don't do this if custom program headers are defined. Otherwise,
@@ -959,30 +964,25 @@ findOrphanPos(SmallVectorImpl<SectionCommand *>::iterator b,
   // better resemble the behavior of GNU ld.
   bool mustAfter = script->hasPhdrsCommands() || !script->memoryRegions.empty();
   if (cast<OutputDesc>(*i)->osec.sortRank <= sec->sortRank || mustAfter) {
-    while (++i != e) {
-      auto *cur = dyn_cast<OutputDesc>(*i);
-      if (cur && cur->osec.hasInputSections &&
-          getRankProximity(sec, cur) != proximity)
+    for (auto j = ++i; j != e; ++j) {
+      if (!isOutputSecWithInputSections(*j))
+        continue;
+      if (getRankProximity(sec, *j) != proximity)
         break;
+      i = j + 1;
     }
+  } else {
+    for (; i != b; --i)
+      if (isOutputSecWithInputSections(i[-1]))
+        break;
   }
 
-  auto isOutputSecWithInputSections = [](SectionCommand *cmd) {
-    auto *osd = dyn_cast<OutputDesc>(cmd);
-    return osd && osd->osec.hasInputSections;
-  };
-  auto j =
-      std::find_if(std::make_reverse_iterator(i), std::make_reverse_iterator(b),
-                   isOutputSecWithInputSections);
-  i = j.base();
-
   // As a special case, if the orphan section is the last section, put
   // it at the very end, past any other commands.
   // This matches bfd's behavior and is convenient when the linker script fully
   // specifies the start of the file, but doesn't care about the end (the non
   // alloc sections for example).
-  auto nextSec = std::find_if(i, e, isOutputSecWithInputSections);
-  if (nextSec == e)
+  if (std::find_if(i, e, isOutputSecWithInputSections) == e)
     return e;
 
   while (i != e && shouldSkip(*i))