[lldb] Unify CalculateMD5 return types (#90921)

# Overview
In my previous PR: https://github.com/llvm/llvm-project/pull/88812,
@JDevlieghere suggested to match return types of the various calculate
md5 functions.

This PR achieves that by changing the various calculate md5 functions to
return `llvm::ErrorOr<llvm::MD5::MD5Result>`.
 
The suggestion was to go for `std::optional<>` but I opted for
`llvm::ErrorOr<>` because local calculate md5 was already possibly
returning `ErrorOr`.

To make sure I didn't break the md5 calculation functionality, I ran
some tests for the gdb remote client, and things seem to work.

# Testing
1. Remote file doesn't exist

![image](https://github.com/llvm/llvm-project/assets/1326275/b26859e2-18c3-4685-be8f-c6b6a5a4bc77)

1. Remote file differs

![image](https://github.com/llvm/llvm-project/assets/1326275/cbdb3c58-555a-401b-9444-c5ff4c04c491)

1. Remote file matches

![image](https://github.com/llvm/llvm-project/assets/1326275/07561572-22d1-4e0a-988f-bc91b5c2ffce)

## Test gaps
Unfortunately, I had to modify
`lldb/source/Plugins/Platform/MacOSX/PlatformDarwinDevice.cpp` and I
can't test the changes there. Hopefully, the existing test suite / code
review from whomever is reading this will catch any issues.

Co-authored-by: Anthony Ha <antha@microsoft.com>

1 files changed, 16 insertions, 20 deletions

diff --git a/lldb/source/Target/Platform.cpp b/lldb/source/Target/Platform.cpp
index 91483ba008f4..4af4aa68ccd0 100644
--- a/lldb/source/Target/Platform.cpp
+++ b/lldb/source/Target/Platform.cpp
@@ -1199,22 +1199,22 @@ Status Platform::PutFile(const FileSpec &source, const FileSpec &destination,
   Status error;
 
   bool requires_upload = true;
-  uint64_t dest_md5_low, dest_md5_high;
-  bool success = CalculateMD5(destination, dest_md5_low, dest_md5_high);
-  if (!success) {
-    LLDB_LOGF(log, "[PutFile] couldn't get md5 sum of destination");
+  llvm::ErrorOr<llvm::MD5::MD5Result> remote_md5 = CalculateMD5(destination);
+  if (std::error_code ec = remote_md5.getError()) {
+    LLDB_LOG(log, "[PutFile] couldn't get md5 sum of destination: {0}",
+             ec.message());
   } else {
-    auto local_md5 = llvm::sys::fs::md5_contents(source.GetPath());
-    if (!local_md5) {
-      LLDB_LOGF(log, "[PutFile] couldn't get md5 sum of source");
+    llvm::ErrorOr<llvm::MD5::MD5Result> local_md5 =
+        llvm::sys::fs::md5_contents(source.GetPath());
+    if (std::error_code ec = local_md5.getError()) {
+      LLDB_LOG(log, "[PutFile] couldn't get md5 sum of source: {0}",
+               ec.message());
     } else {
-      const auto [local_md5_high, local_md5_low] = local_md5->words();
       LLDB_LOGF(log, "[PutFile] destination md5: %016" PRIx64 "%016" PRIx64,
-                dest_md5_high, dest_md5_low);
+                remote_md5->high(), remote_md5->low());
       LLDB_LOGF(log, "[PutFile]       local md5: %016" PRIx64 "%016" PRIx64,
-                local_md5_high, local_md5_low);
-      requires_upload =
-          local_md5_high != dest_md5_high || local_md5_low != dest_md5_low;
+                local_md5->high(), local_md5->low());
+      requires_upload = *remote_md5 != *local_md5;
     }
   }
 
@@ -1339,15 +1339,11 @@ lldb_private::Status Platform::RunShellCommand(
   return Status("unable to run a remote command without a platform");
 }
 
-bool Platform::CalculateMD5(const FileSpec &file_spec, uint64_t &low,
-                            uint64_t &high) {
+llvm::ErrorOr<llvm::MD5::MD5Result>
+Platform::CalculateMD5(const FileSpec &file_spec) {
   if (!IsHost())
-    return false;
-  auto Result = llvm::sys::fs::md5_contents(file_spec.GetPath());
-  if (!Result)
-    return false;
-  std::tie(high, low) = Result->words();
-  return true;
+    return std::make_error_code(std::errc::not_supported);
+  return llvm::sys::fs::md5_contents(file_spec.GetPath());
 }
 
 void Platform::SetLocalCacheDirectory(const char *local) {