make install doesn't install target's rustlibs

[sezaru]

When compiling rust with targets for both x86_64-unknown-linux-gnu and i686-unknown-linux-gnu, both rustlibs will be compiled and stored inside stage2-std, but only x86_64 ones will be installed when issuing the make install command.

Here are the steps I'm doing:

./configure --prefix="$(pwd)/image/usr" \
            --libdir="$(pwd)/image/usr/lib64/rust-1.15.1" \
            --mandir="$(pwd)/image/usr/share/rust-1.15.1/man" \
            --release-channel=stable \
            --disable-manage-submodules \
            --default-linker=x86_64-pc-linux-gnu-gcc \
            --default-ar=x86_64-pc-linux-gnu-ar \
            --python=python2.7 \
            --disable-rpath \
            --enable-local-rust \
            --local-rust-root="../stage0" \
            --target=x86_64-unknown-linux-gnu,i686-unknown-linux-gnu \
            --enable-clang \
            --enable-optimize \
            --enable-optimize-cxx \
            --enable-optimize-llvm \
            --enable-optimize-tests \
            --enable-libcpp \
            --llvm-root=/usr \
            --enable-llvm-link-shared
make dist
make install

Note the --target=x86_64-unknown-linux-gnu,i686-unknown-linux-gnu on the configure command.

Here is the stage2-std rustlib directory:

$ ls ./build/tmp/dist/rust-std-1.15.1-i686-unknown-linux-gnu/rust-std-i686-unknown-linux-gnu/lib/rustlib
    i686-unknown-linux-gnu

$ ls ./build/x86_64-unknown-linux-gnu/stage2-std
    i686-unknown-linux-gnu
    release
    x86_64-unknown-linux-gnu

Here is the rustlibs directory after make install

$ ls ./image/usr/lib64/rust-1.15.1/rustlib/
    components
    manifest-rustc
    rust-installer-version
    etc
    manifest-rust-docs
    uninstall.sh
    install.log
    manifest-rust-std-x86_64-unknown-linux-gnu
    x86_64-unknown-linux-gnu

[alexcrichton]

I believe this is a dupe of #39235 but thanks for the report!