prepared for build in a docker instance on jenkins

ax_init_standard_project.m4

@@ -696,3 +696,15 @@ AC_DEFUN([AX_CHECK_VALID_LD_FLAG], [
   AC_SUBST(LDFLAGS)
   AC_MSG_RESULT([$newflag in $LDFLAGS])
 ])
+
+# Check if a package exists in the current distribution, if yes, require it
+# in debian/control.in append @DEB_DEPEND_IFEXISTS@ to Build-Depends
+#  - parameter:
+#     $1 = package name
+AC_DEFUN([AX_DEB_DEPEND_IFEXISTS], [
+  pkg=$1
+  if test -n "$(apt-cache policy -q ${pkg} 2> /dev/null)"; then
+     DEB_DEPEND_IFEXISTS+=", ${pkg}"
+  fi
+  AC_SUBST(DEB_DEPEND_IFEXISTS)
+])