sci-mathematics/gmm: Build in C++14 mode

Bug: https://bugs.gentoo.org/show_bug.cgi?id=612294
Package-Manager: Portage-2.3.5, Repoman-2.3.2

sci-mathematics/gmm/gmm-5.1.ebuild

@@ -3,6 +3,8 @@
 
 EAPI=6
 
+inherit flag-o-matic
+
 DESCRIPTION="Generic C++ template library for sparse, dense and skyline matrices"
 SRC_URI="http://download.gna.org/getfem/stable/${P}.tar.gz"
 HOMEPAGE="http://www-gmm.insa-toulouse.fr/getfem/"
@@ -11,3 +13,10 @@ LICENSE="|| ( LGPL-3 LGPL-3-with-linking-exception )"
 SLOT="0"
 KEYWORDS="amd64 ~arm ~hppa ~ppc ~ppc64 x86 ~x86-fbsd ~amd64-linux ~x86-linux"
 IUSE=""
+
+src_configure() {
+	# required for tests, #612294
+	append-cxxflags -std=c++14
+
+	default
+}