distro/yocto: add meta-salmanoff Yocto layer for QEMU x86 images

Vendor the BitBake layer (recipes, network config, boost pin, kernel
append, runqemu bridge script) alongside SMO for packaging as a Yocto image.

Co-authored-by: Cursor <cursoragent@cursor.com>

distro/yocto/meta-salmanoff/conf/layer.conf

@@ -0,0 +1,17 @@
+BBPATH .= ":${LAYERDIR}"
+
+BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
+           ${LAYERDIR}/recipes-*/*/*.bbappend"
+
+BBFILE_COLLECTIONS += "salmanoff"
+BBFILE_PATTERN_salmanoff = "^${LAYERDIR}/"
+BBFILE_PRIORITY_salmanoff = "10"
+
+LAYERSERIES_COMPAT_salmanoff = "wrynose"
+
+# Salmanoff requires shared Boost.System (< 1.89). Pin 1.86 from this layer.
+BBMASK += ".*/boost_1.90.0.bb"
+BBMASK += ".*/boost-build-native_1.90.0.bb"
+PREFERRED_VERSION_boost = "1.86.%"
+PREFERRED_VERSION_boost-build-native = "1.86.%"
+