Functions only called by DumpFreeSpace need to be conditionally compiled.

src/client/linux/microdump_writer/microdump_writer.cc

Index: src/client/linux/microdump_writer/microdump_writer.cc
diff --git a/src/client/linux/microdump_writer/microdump_writer.cc b/src/client/linux/microdump_writer/microdump_writer.cc
index 2091429c62f2b27a1c693204092fcaa782fb9344..ba10ee3a602c1ef920bf48b786645f200aa9b138 100644
--- a/src/client/linux/microdump_writer/microdump_writer.cc
+++ b/src/client/linux/microdump_writer/microdump_writer.cc
@@ -62,6 +62,10 @@ using google_breakpad::UContextReader;
 
 const size_t kLineBufferSize = 2048;
 
+#if !defined(__LP64__)
+// The following are only used by DumpFreeSpace, so need to be compiled
+// in conditionally in the same way.
+
 template <typename Dst, typename Src>
 Dst saturated_cast(Src src) {
   if (src >= std::numeric_limits<Dst>::max())
@@ -122,6 +126,8 @@ size_t NextOrderedMapping(
   return best;
 }
 
+#endif  // !__LP64__
+
 class MicrodumpWriter {
  public:
   MicrodumpWriter(const ExceptionHandler::CrashContext* context,