Save machine ident in captures and compare to machine ident on open

* If the machine idents differ in significant ways that we'd consider
  it to be a different platform (currently just OS), and if so mark it
  as supported but suggested to be replayed remotely.

renderdoc/serialise/serialiser.cpp

@@ -1450,6 +1450,24 @@ void Serialiser::FlushToDisk()
       SAFE_DELETE_ARRAY(symbolDB);
     }
 
+    // write the machine identifier as an ASCII section
+    {
+      const char sectionName[] = "renderdoc/internal/machineid";
+
+      uint64_t machineID = OSUtility::GetMachineIdent();
+
+      BinarySectionHeader section = {0};
+      section.isASCII = 0;                                // redundant but explicit
+      section.sectionNameLength = sizeof(sectionName);    // includes null terminator
+      section.sectionType = eSectionType_MachineID;
+      section.sectionFlags = eSectionFlag_None;
+      section.sectionLength = sizeof(machineID);
+
+      FileIO::fwrite(&section, 1, offsetof(BinarySectionHeader, name), binFile);
+      FileIO::fwrite(sectionName, 1, sizeof(sectionName), binFile);
+      FileIO::fwrite(&machineID, 1, sizeof(machineID), binFile);
+    }
+
     FileIO::fclose(binFile);
   }
 }

renderdoc/serialise/serialiser.h

@@ -180,6 +180,7 @@ public:
     eSectionType_Unknown = 0,
     eSectionType_FrameCapture,       // renderdoc/internal/framecapture
     eSectionType_ResolveDatabase,    // renderdoc/internal/resolvedb
+    eSectionType_MachineID,          // renderdoc/internal/machineid
     eSectionType_FrameBookmarks,     // renderdoc/ui/bookmarks
     eSectionType_Notes,              // renderdoc/ui/notes
     eSectionType_Num,
@@ -281,6 +282,22 @@ public:
   Callstack::StackResolver *GetCallstackResolver() { return m_pResolver; }
   void SetCallstack(uint64_t *levels, size_t numLevels);
 
+  uint64_t GetSavedMachineIdent()
+  {
+    Section *id = m_KnownSections[eSectionType_MachineID];
+
+    // section might not be present on older captures (or if it was stripped out
+    // by someone over-eager to remove information)
+    if(id != NULL && id->data.size() >= sizeof(uint64_t))
+    {
+      uint64_t ident = 0;
+      memcpy(&ident, &id->data[0], sizeof(ident));
+      return ident;
+    }
+
+    return 0;
+  }
+
   // get the callstack associated with the last scope
   Callstack::Stackwalk *GetLastCallstack()
   {