Revert "Remove V8_HOST_CAN_READ_UNALIGNED and its uses."

src/snapshot-source-sink.cc

Index: src/snapshot-source-sink.cc
diff --git a/src/snapshot-source-sink.cc b/src/snapshot-source-sink.cc
index 44f87060fc98f478926fe5a15f9130c1d56cdbca..2be14383fa6009f247f0a770ed370154422d5679 100644
--- a/src/snapshot-source-sink.cc
+++ b/src/snapshot-source-sink.cc
@@ -24,10 +24,14 @@ SnapshotByteSource::~SnapshotByteSource() { }
 
 int32_t SnapshotByteSource::GetUnalignedInt() {
   DCHECK(position_ < length_);  // Require at least one byte left.
+#if defined(V8_HOST_CAN_READ_UNALIGNED) &&  __BYTE_ORDER == __LITTLE_ENDIAN
+  int32_t answer = *reinterpret_cast<const int32_t*>(data_ + position_);
+#else
   int32_t answer = data_[position_];
   answer |= data_[position_ + 1] << 8;
   answer |= data_[position_ + 2] << 16;
   answer |= data_[position_ + 3] << 24;
+#endif
   return answer;
 }