[sanitizer] Fix s390 build after r334900

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@334913 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/sanitizer_common/sanitizer_linux_s390.cc b/lib/sanitizer_common/sanitizer_linux_s390.cc
index a6da82e..ad8c87f 100644
--- a/lib/sanitizer_common/sanitizer_linux_s390.cc
+++ b/lib/sanitizer_common/sanitizer_linux_s390.cc
@@ -126,7 +126,7 @@
   // This should never fail, but just in case...
   if (uname(&buf))
     return false;
-  char *ptr = buf.release;
+  const char *ptr = buf.release;
   major = internal_simple_strtoll(ptr, &ptr, 10);
   // At least first 2 should be matched.
   if (ptr[0] != '.')