vscode: switch S to UNPACKDIR for whinlatter+

Whinlatter and wrynose split WORKDIR and UNPACKDIR; do_unpack
extracts under UNPACKDIR while WORKDIR is reserved for build
artefacts. The recipe used to set S = ${WORKDIR}/VSCode-linux-...
which now produces 'S should be set relative to UNPACKDIR' as a
fatal error.

Switch to S = ${UNPACKDIR}/... with a kirkstone..walnascar
fallback via UNPACKDIR ??= ${WORKDIR} so older releases that
don't define UNPACKDIR keep working.

Author: EmbeddedAndroid

recipes-devtools/vscode/vscode_1.120.0.bb

@@ -44,7 +44,12 @@ SRC_URI[vscode-x64.sha256sum]   = "510426eb23d330bf25d84fe88e49a08d965d6b21957b8
 SRC_URI[vscode-arm64.sha256sum] = "69c0d1d0534cd4173e2b3dbee5d001ed5c2bd0c846bb22dca917312b64eb1baf"
 SRC_URI[vscode-armhf.sha256sum] = "1662d3dd08a3602544bc4ca1b091e04d5393a23414607b7c34f0570ebd0d5daa"
 
-S = "${WORKDIR}/VSCode-linux-${VSCODE_ARCH}"
+# Whinlatter+ split WORKDIR / UNPACKDIR; tarballs land under UNPACKDIR
+# while WORKDIR is now reserved for build artefacts. Older releases
+# (kirkstone..walnascar) didn't have UNPACKDIR at all -- give it a
+# WORKDIR fallback so the recipe works on every supported release.
+UNPACKDIR ??= "${WORKDIR}"
+S = "${UNPACKDIR}/VSCode-linux-${VSCODE_ARCH}"
 
 # These are arch-specific prebuilt ELFs, not noarch content; bin_package
 # inherits allarch which is wrong here. Override back to per-machine