build: bump to use c++17

Bump build to use c++17.

Change-Id: If75df125e900871151d3e723b0580e94063a6e28
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index 5cdc946..95113d9 100755
--- a/configure.ac
+++ b/configure.ac
@@ -7,11 +7,12 @@
 
 # Checks for programs.
 AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX_14([noext])
 AM_PROG_AR
 AC_PROG_INSTALL
 AC_PROG_MAKE_SET
 
+AX_CXX_COMPILE_STDCXX_17([noext])
+
 LT_INIT
 
 # Checks for libraries.