[vala] build: Bump bootstrap requirement to 0.39.6 for --abi-stability build flag

[Rico Tzschichholz <ricotz src gnome org>]

commit e373e60b13533414c5b27c1645f7247158042a32
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Fri Jan 19 17:23:07 2018 +0100

    build: Bump bootstrap requirement to 0.39.6 for --abi-stability build flag

 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 3471391..8acaf03 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,7 +51,7 @@ fi
 AC_PATH_PROG(VALAC, valac, valac)
 AC_SUBST(VALAC)
 
-VALAC_BOOTSTRAP_REQUIRED=0.25.1
+VALAC_BOOTSTRAP_REQUIRED=0.39.5.8
 
 AS_IF([test "$VALAC" != valac], [FOUND_VALAC_VERION=`$VALAC --version | sed 's/Vala  *//'`
        AS_VERSION_COMPARE(["$VALAC_BOOTSTRAP_REQUIRED"], ["$FOUND_VALAC_VERION"],
@@ -59,7 +59,7 @@ AS_IF([test "$VALAC" != valac], [FOUND_VALAC_VERION=`$VALAC --version | sed 's/V
 
 VALAFLAGS="$VALAFLAGS --disable-version-header"
 if test x$enable_boostrap = xyes; then
-       VALAFLAGS="$VALAFLAGS --hide-internal"
+       VALAFLAGS="$VALAFLAGS --hide-internal --abi-stability"
 fi
 
 AC_SUBST(VALAFLAGS)