meta-phosphor: Enable Software Bill of Materials (SBOM)

SBOM support gives a conscise, structured summary of the content of the
image and the licenses used.

More information is provided here:

https://docs.yoctoproject.org/next/dev-manual/sbom.html

Change-Id: Ia0f906b6e2994c030b30cc73c19b5f74b326cda5
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/meta-phosphor/conf/distro/include/phosphor-base.inc b/meta-phosphor/conf/distro/include/phosphor-base.inc
index 9d5c7e1..3a1a56f 100644
--- a/meta-phosphor/conf/distro/include/phosphor-base.inc
+++ b/meta-phosphor/conf/distro/include/phosphor-base.inc
@@ -143,3 +143,6 @@
 OBMC_ORG_YAML_SUBDIRS += " org/freedesktop xyz/openbmc_project"
 
 PREFERRED_VERSION_libgpiod = "1.6.4"
+
+# Enable SBOM: https://docs.yoctoproject.org/next/dev-manual/sbom.html
+INHERIT += "create-spdx"