[memprof] Avoid meaningless pod copy

[yingcong-wu]

Summary

The pointer Buffer is not changed, so there is no need to use reference, and the Pod here should use reference to avoid meaningless copy.

[yingcong-wu]

add const to pod

[snehasish]

LGTM. Let me know if you like this to be committed by proxy.

[yingcong-wu]

In D145024#4163082, @snehasish wrote:

LGTM. Let me know if you like this to be committed by proxy.

Thanks @snehasish. I don’t have commit access, can you land this patch for me?

compiler-rt/lib/memprof/memprof_rawprofile.cpp

 
 namespace __memprof {
 using ::__sanitizer::Vector;
 using ::llvm::memprof::MemInfoBlock;
 using SegmentEntry = ::llvm::memprof::SegmentEntry;
 using Header = ::llvm::memprof::Header;
 
 namespace {
-template <class T> char *WriteBytes(T Pod, char *&Buffer) {
+template <class T> char *WriteBytes(const T &Pod, char *Buffer) {
   *(T *)Buffer = Pod;
   return Buffer + sizeof(T);
 }
 
 void RecordStackId(const uptr Key, UNUSED LockedMemInfoBlock *const &MIB,
                    void *Arg) {
   // No need to touch the MIB value here since we are only recording the key.
   auto *StackIds = reinterpret_cast<Vector<u64> *>(Arg);