recipes: Switch away from S = WORKDIR

Where recipes use S = ${WORKDIR}, change them to set UNPACKDIR to
a subdir of WORKDIR and make S point at this instead.

I've chosen not to force S into any standard UNPACKDIR we may pick in
future just so the S = UNPACKDIR case is clearly visible by the
directory naming under WORKDIR as that should aid usability.

(From OE-Core rev: d9328e3b0b062f0621de3d114584b44f384a1c02)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/initrdscripts/initramfs-live-install_1.0.bb

@@ -3,8 +3,8 @@ LICENSE = "MIT"
 LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
 SRC_URI = "file://init-install.sh"
 
-
-S = "${WORKDIR}"
+S = "${WORKDIR}/sources"
+UNPACKDIR = "${S}"
 
 RDEPENDS:${PN} = "grub parted e2fsprogs-mke2fs util-linux-blkid ${VIRTUAL-RUNTIME_base-utils}"
 RRECOMMENDS:${PN} = "${VIRTUAL-RUNTIME_base-utils-syslog}"