os-release: add os-release-initrd package

When systemd is used inside an initramfs, it uses the presence of
`/etc/initrd-release` to detect when the system is in the initrd phase.
Otherwise `/etc/initrd-release` has the same format as
`/etc/os-release`.

Add `os-release-initrd` package to provide `/etc/initrd-release` as a
symlink to the os-release file. To avoid adding this file to the
`os-release` package, explicitly only add `/etc/os-release` to the
`os-release` package.

(From OE-Core rev: 6311fb6f412ef923cc0b34a821e875990fc043f5)

Signed-off-by: Claudius Heine <ch@denx.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/os-release/os-release.bb

@@ -50,6 +50,11 @@ do_install () {
     install -d ${D}${nonarch_libdir} ${D}${sysconfdir}
     install -m 0644 os-release ${D}${nonarch_libdir}/
     ln -rs ${D}${nonarch_libdir}/os-release ${D}${sysconfdir}/os-release
+    ln -rs ${D}${nonarch_libdir}/os-release ${D}${sysconfdir}/initrd-release
 }
 
-FILES:${PN} += "${nonarch_libdir}/os-release"
+FILES:${PN} = "${sysconfdir}/os-release ${nonarch_libdir}/os-release"
+
+PACKAGES += "${PN}-initrd"
+FILES:${PN}-initrd = "${sysconfdir}/initrd-release"
+RDEPENDS:${PN}-initrd += "${PN}"