[lld] Use std::size instead of llvm::array_lengthof

[jloser]

Summary

LLVM contains a helpful function for getting the size of a C-style
array: llvm::array_lengthof. This is useful prior to C++17, but not as
helpful for C++17 or later: std::size already has support for C-style
arrays.

[jloser]

clang-format

lld/COFF/Chunks.cpp

 #include "llvm/ADT/Twine.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/BinaryFormat/COFF.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
+#include <iterator>
 
 using namespace llvm;
 using namespace llvm::object;
 using namespace llvm::support::endian;
 using namespace llvm::COFF;
 using llvm::support::ulittle32_t;
 
 namespace lld::coff {

 MergeChunk::MergeChunk(uint32_t alignment)
     : builder(StringTableBuilder::RAW, alignment) {
   setAlignment(alignment);
 }
 
 void MergeChunk::addSection(COFFLinkerContext &ctx, SectionChunk *c) {
   assert(isPowerOf2_32(c->getAlignment()));
   uint8_t p2Align = llvm::Log2_32(c->getAlignment());
-  assert(p2Align < array_lengthof(ctx.mergeChunkInstances));
+  assert(p2Align < std::size(ctx.mergeChunkInstances));
   auto *&mc = ctx.mergeChunkInstances[p2Align];
   if (!mc)
     mc = make<MergeChunk>(c->getAlignment());
   mc->sections.push_back(c);
 }
 
 void MergeChunk::finalizeContents() {
   assert(!finalized && "should only finalize once");