configure: add AC_C_CONST to configure.ac

This is inspired by the autobook sections on Windows DLL builds.
https://www.sourceware.org/autobook/autobook/autobook_137.html

The AC_C_CONST macro improves support for the C language 'const'
decoration in case the compiler does not understand it.

diff --git a/configure.ac b/configure.ac
index d59e0bea35ee64618169ce4feac351559ab5cfa2..3a8b163da3f2a57e99216c856bd2690e28332e9f 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -40,6 +40,8 @@ AC_PROG_CC
 AC_PROG_INSTALL
 AC_PROG_LN_S
 
+AC_C_CONST
+
 # Required for per-target flags or subdir-objects with C sources.
 AM_PROG_CC_C_O