dev-db/opendbx: workaround build failure with GCC 11 in 1.4.6-r3

Closes: https://bugs.gentoo.org/788304
Signed-off-by: Sam James <sam@gentoo.org>

dev-db/opendbx/opendbx-1.4.6-r3.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2020 Gentoo Authors
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI="6"
@@ -68,6 +68,9 @@ src_configure() {
 		append-ldflags -L"${ORACLE_HOME}"
 	fi
 
+	# bug #788304
+	append-cxxflags -std=c++14
+
 	econf --with-backends="${backends}" --enable-manpages="$(usex man yes no)"
 }