Add link time optimization support to makepkg

Add the 'lto' option to enable building with link time optimization
by adding '-flto' to both CFLAGS and CXXFLAGS.  The 'lto' option can
be specificed both in the PKGBUILD or by setting the default in
makepkg.conf.

Signed-off-by: Allan McRae <allan@archlinux.org>

2 files changed, 38 insertions, 0 deletions

diff --git a/scripts/libmakepkg/buildenv/lto.sh.in b/scripts/libmakepkg/buildenv/lto.sh.in
new file mode 100644
index 00000000..8e7be66a
--- /dev/null
+++ b/scripts/libmakepkg/buildenv/lto.sh.in
@@ -0,0 +1,37 @@
+#!/usr/bin/bash
+#
+#   lto.sh - Specify flags for building a package with link-time
+#            optimisation
+#
+#   Copyright (c) 2021 Pacman Development Team <pacman-dev@archlinux.org>
+#
+#   This program is free software; you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation; either version 2 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+[[ -n "$LIBMAKEPKG_BUILDENV_LTO_SH" ]] && return
+LIBMAKEPKG_BUILDENV_LTO_SH=1
+
+LIBRARY=${LIBRARY:-'@libmakepkgdir@'}
+
+source "$LIBRARY/util/option.sh"
+
+build_options+=('lto')
+buildenv_functions+=('buildenv_lto')
+
+buildenv_lto() {
+	if check_option "lto" "y"; then
+		CFLAGS+=" -flto"
+		CXXFLAGS+=" -flto"
+	fi
+}
diff --git a/scripts/libmakepkg/buildenv/meson.build b/scripts/libmakepkg/buildenv/meson.build
index 34d4ba7b..b72d91c0 100644
--- a/scripts/libmakepkg/buildenv/meson.build
+++ b/scripts/libmakepkg/buildenv/meson.build
@@ -4,6 +4,7 @@ sources = [
   'buildflags.sh.in',
   'compiler.sh.in',
   'debugflags.sh.in',
+  'lto.sh.in',
   'makeflags.sh.in',
 ]