rust: drop local-rust PACKAGECONFIG

This drops the ability to supply your own rust through the PACKAGECONFIG
local-rust option. This isn't tested and we really need to better expand
support for build arches. At the same time this simplifies how the rust
stage0 snapshot is extracted and used by the build system.

recipes-devtools/rust/rust.inc

@@ -8,24 +8,13 @@ inherit rust
 
 SRC_URI = "\
 	https://static.rust-lang.org/dist/rustc-${PV}-src.tar.gz;name=rust \
+	https://static.rust-lang.org/dist/${RUST_SNAPSHOT}.tar.gz;name=rust-snapshot \
     "
 
 S = "${WORKDIR}/rustc-${PV}"
 
 DEPENDS += "file-native"
 
-PACKAGECONFIG ??= ""
-
-# Controls whether we use the local rust to build.
-# By default, we use the rust-snapshot. In some cases (non-supported host
-# systems) this may not be possible.  In other cases, it might be desirable
-# to have rust-cross built using rust-native.
-PACKAGECONFIG[local-rust] = ""
-
-FETCH_STAGE0 = "${@bb.utils.contains('PACKAGECONFIG', 'local-rust', 'false', 'true', d)}"
-
-SRC_URI += "${@bb.utils.contains('PACKAGECONFIG', 'local-rust', '', '${RUST_SNAPSHOT_URI};unpack=0;name=rust-snapshot', d)}"
-
 # We generate local targets, and need to be able to locate them
 export RUST_TARGET_PATH="${WORKDIR}/targets/"
 
@@ -393,18 +382,7 @@ do_configure () {
     # where we're reinstalling the compiler. May want to try for a real
     # path based on bitbake vars
     # Also will be wrong when relative libdir and/or bindir aren't 'bin' and 'lib'.
-    local_rust_root=/not/set/do/not/use
-    if ${FETCH_STAGE0}; then
-        mkdir -p dl
-        tar -xf ${WORKDIR}/${RUST_SNAPSHOT} -C dl
-        ./dl/rustc-${RS_VERSION}-${RS_ARCH}/install.sh --prefix=$PWD/dl
-        local_rust_root="$PWD/dl"
-    elif which rustc >/dev/null 2>&1; then
-        local_rustc=$(which rustc)
-        if [ -n "$local_rustc" ]; then
-            local_rust_root=$(dirname $(dirname $local_rustc))
-        fi
-    fi
+    local_rust_root="$PWD/dl"
 
     # - rpath is required otherwise rustc fails to resolve symbols
     # - submodule management is done by bitbake's fetching
@@ -431,7 +409,8 @@ do_configure () {
         "--libdir=${libdir}"                \
         "--bindir=${bindir}"                \
         "--platform-cfg=${WORKDIR}/mk-cfg/" \
-        "--enable-local-rust --local-rust-root=$local_rust_root" \
+        "--enable-local-rust"               \
+        "--local-rust-root=${WORKDIR}/${RUST_SNAPSHOT}/rustc" \
         ${EXTRA_OECONF}
 }