ci: move all x86_64 runners to the host-x86_64 directory

We need to add runners designed for an aarch64 host system, and it'd be
nice to return an error message if someone tries to run an image
designed for an host architecture in another one.

To start the work on this, this commit moves all the existing builders
in the host-x86_64 directory, and changes the run.sh script to look up
the image in the correct directory based on the host architecture.

Author: pietroalbini

.github/workflows/ci.yml

@@ -428,7 +428,7 @@ jobs:
             os: windows-latest-xl
           - name: x86_64-msvc-tools
             env:
-              SCRIPT: src/ci/docker/x86_64-gnu-tools/checktools.sh x.py /tmp/toolstate/toolstates.json windows
+              SCRIPT: src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh x.py /tmp/toolstate/toolstates.json windows
               RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-msvc --save-toolstates=/tmp/toolstate/toolstates.json"
             os: windows-latest-xl
           - name: i686-mingw-1

src/ci/azure-pipelines/auto.yml

@@ -151,7 +151,7 @@ jobs:
         NO_LLVM_ASSERTIONS: 1
       # MSVC tools tests
       x86_64-msvc-tools:
-        SCRIPT: src/ci/docker/x86_64-gnu-tools/checktools.sh x.py
+        SCRIPT: src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh x.py
         INITIAL_RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-msvc --save-toolstates=/tmp/toolstate/toolstates.json
 
       # 32/64-bit MinGW builds.

src/ci/docker/README.md

@@ -20,7 +20,7 @@ RUN dpkg --add-architecture i386 && \
 
 COPY scripts/android-sdk.sh /scripts/
 COPY scripts/android-sdk-manager.py /scripts/
-COPY arm-android/android-sdk.lock /android/sdk/android-sdk.lock
+COPY host-x86_64/arm-android/android-sdk.lock /android/sdk/android-sdk.lock
 RUN /scripts/android-sdk.sh
 
 ENV PATH=$PATH:/android/sdk/emulator

src/ci/docker/arm-android/Dockerfile renamed to src/ci/docker/host-x86_64/arm-android/Dockerfile

@@ -31,7 +31,7 @@ WORKDIR /build
 # The `vexpress_config` config file was a previously generated config file for
 # the kernel. This file was generated by running `make vexpress_defconfig`
 # followed by `make menuconfig` and then enabling the IPv6 protocol page.
-COPY armhf-gnu/vexpress_config /build/.config
+COPY host-x86_64/armhf-gnu/vexpress_config /build/.config
 RUN curl https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.4.42.tar.xz | \
       tar xJf - && \
       cd /build/linux-4.4.42 && \

src/ci/docker/arm-android/android-sdk.lock renamed to src/ci/docker/host-x86_64/arm-android/android-sdk.lock

@@ -31,7 +31,7 @@ WORKDIR /build
 # The `config` config file was a previously generated config file for
 # the kernel. This file was generated by running `make defconfig`
 # followed by `make menuconfig` and then enabling the IPv6 protocol page.
-COPY aarch64-gnu/config /build/.config
+COPY host-x86_64/aarch64-gnu/config /build/.config
 RUN curl https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.4.42.tar.xz | \
       tar xJf - && \
       cd /build/linux-4.4.42 && \