tools: updater: iterate via string instead of auto

Use a std::string declaration instead of auto to add backwards
compatibility and because it's clearly only ever going to be a string
and we're doing a c-string check.

Change-Id: I89bf9076cdc711209a75684a984a39c058367355
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/tools/updater.cpp b/tools/updater.cpp
index 0c45d7b..2620715 100644
--- a/tools/updater.cpp
+++ b/tools/updater.cpp
@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <cstring>
 #include <memory>
+#include <string>
 
 namespace host_tool
 {
@@ -41,7 +42,7 @@
      */
     std::vector<std::string> blobs = blob->getBlobList();
     auto blobInst = std::find_if(
-        blobs.begin(), blobs.end(), [&goalFirmware](const auto& iter) {
+        blobs.begin(), blobs.end(), [&goalFirmware](const std::string& iter) {
             /* Running into weird scenarios where the string comparison doesn't
              * work.  TODO: revisit.
              */