Address const issues in preparation for libcxx rebase.

Change-Id: I5199c1eb4e874fd354beefa1232707949483e88d
diff --git a/Utils.cpp b/Utils.cpp
index e4f473a..a9bddfa 100644
--- a/Utils.cpp
+++ b/Utils.cpp
@@ -211,7 +211,7 @@
     for (auto line : output) {
         // Extract values from blkid output, if defined
         const char* cline = line.c_str();
-        char* start = strstr(cline, "TYPE=");
+        const char* start = strstr(cline, "TYPE=");
         if (start != nullptr && sscanf(start + 5, "\"%127[^\"]\"", value) == 1) {
             fsType = value;
         }