build with rust fails

[hgy59]

It is not possible to build packages with rust anymore.

This must be related to #5441

example output of make arch-x64-6.1 to build dua.

===>  Compiling for dua
  ==> Cargo build rust package dua
PKG_CONFIG_LIBDIR=/spksrc/diyspk/dua/work-x64-6.1/install//var/packages/dua/target/lib/pkgconfig WORK_DIR=/spksrc/diyspk/dua/work-x64-6.1 INSTALL_PREFIX=/var/packages/dua/target TC=syno-x64-6.1 SYSROOT="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/x86_64-pc-linux-gnu/sys-root" LD="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ld" LDSHARED="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-gcc -shared" CPP="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-cpp" NM="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-nm" CC="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-gcc" AS="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-as" RANLIB="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ranlib" CXX="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-g++" AR="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ar" STRIP="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-strip" OBJDUMP="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-objdump" READELF="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-readelf" CFLAGS="-I/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/x86_64-pc-linux-gnu/sys-root/usr/include -I/spksrc/diyspk/dua/work-x64-6.1/install//var/packages/dua/target/include " CPPFLAGS="-I/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/x86_64-pc-linux-gnu/sys-root/usr/include -I/spksrc/diyspk/dua/work-x64-6.1/install//var/packages/dua/target/include " CXXFLAGS="-I/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/x86_64-pc-linux-gnu/sys-root/usr/include -I/spksrc/diyspk/dua/work-x64-6.1/install//var/packages/dua/target/include " LDFLAGS="-L/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/x86_64-pc-linux-gnu/sys-root/lib -L/spksrc/diyspk/dua/work-x64-6.1/install//var/packages/dua/target/lib -Wl,--rpath-link,/spksrc/diyspk/dua/work-x64-6.1/install//var/packages/dua/target/lib -Wl,--rpath,/var/packages/dua/target/lib " CARGO_HOME="/opt/cargo" RUSTUP_HOME="/opt/rustup" CARGO_BUILD_TARGET="x86_64-unknown-linux-gnu" CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_AR="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-ar" CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER="/spksrc/toolchain/syno-x64-6.1/work/x86_64-pc-linux-gnu/bin/x86_64-pc-linux-gnu-gcc" cargo build --target=x86_64-unknown-linux-gnu --path /spksrc/diyspk/dua/work-x64-6.1/dua-cli-2.17.2 --root /spksrc/diyspk/dua/work-x64-6.1/install/var/packages/dua/target
error: Found argument '--path' which wasn't expected, or isn't valid in this context

	If you tried to supply `--path` as a value rather than a flag, use `-- --path`

[th0ma7]

When I imported your part of the code I tooked the liberty of changing the build_and_install_target into individual build and install targets which I'm pretty sure is what that is causing your build failure. I know for sure I've overlooked the cross-compiling default rustc behavior.

Code change reference:
https://github.com/SynoCommunity/spksrc/pull/5435/files#diff-ea983e7bc021e1fd10a799e4314542329d6d12854a9509cda2dca87d087cddd4L112-R65