https://github.com/systemd/systemd/commit/c29537f39e4f413a6cbfe9669fa121bdd6d8b36f
https://bugs.gentoo.org/821547

From: Dan Streetman <ddstreet@canonical.com>
Date: Fri, 3 Sep 2021 12:43:33 -0400
Subject: [PATCH] meson.build: change operator combining bools from + to and

upstream meson stopped allowing combining boolean with the plus
operator, and now requires using the logical and operator

reference:
https://github.com/mesonbuild/meson/commit/43302d3296baff6aeaf8e03f5d701b0402e37a6c

Fixes: #20632
--- a/meson.build
+++ b/meson.build
@@ -35,7 +35,7 @@ conf.set10('BUILD_MODE_DEVELOPER', get_option('mode') == 'developer',
 
 want_ossfuzz = get_option('oss-fuzz')
 want_libfuzzer = get_option('llvm-fuzz')
-if want_ossfuzz + want_libfuzzer > 1
+if want_ossfuzz and want_libfuzzer
         error('only one of oss-fuzz or llvm-fuzz can be specified')
 endif