phosphor-defaults: Enable LTO for all meson targets

We want to benefit from the space savings of being able to link time
optimize all of our binaries built through meson.

Change-Id: If36f9e76a27bfa8d00210492c2397a174e09dbd3
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-phosphor/conf/distro/include/phosphor-defaults.inc b/meta-phosphor/conf/distro/include/phosphor-defaults.inc
index b8f4c52..7aed7cb 100644
--- a/meta-phosphor/conf/distro/include/phosphor-defaults.inc
+++ b/meta-phosphor/conf/distro/include/phosphor-defaults.inc
@@ -239,6 +239,9 @@
 # is merged and rev bumped
 SECURITY_CFLAGS_pn-pldm = ""
 
+# We generally want to enable LTO with meson
+EXTRA_OEMESON_append_class-target = " -Db_lto=true"
+
 # Set the root password to '0penBmc'
 inherit extrausers