linuxkit: Remove QEMU Container Backend

This commit removes the container backend for QEMU.
QEMU and it's tools are available on all platforms.

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>

tools/qemu/Dockerfile

@@ -1,26 +0,0 @@
-FROM linuxkit/alpine:86cd4f51b49fb9a078b50201d892a3c7973d48ec AS mirror
-RUN mkdir -p /out/etc/apk && cp -r /etc/apk/* /out/etc/apk/
-RUN apk add --no-cache --initdb -p /out \
-    alpine-baselayout \
-    busybox \
-    libarchive-tools \
-    qemu-img && \
-    case $(uname -m) in \
-    x86_64) \
-        apk add --no-cache --initdb -p /out qemu-system-x86_64 ovmf; \
-        ;; \
-    aarch64) \
-        apk add --no-cache --initdb -p /out qemu-system-aarch64; \
-        ;; \
-    s390x) \
-        apk add --no-cache --initdb -p /out qemu-system-s390x; \
-        ;; \
-    esac
-RUN rm -rf /out/etc/apk /out/lib/apk /out/var/cache
-
-FROM scratch
-ENTRYPOINT []
-CMD []
-WORKDIR /
-COPY --from=mirror /out/ /
-

tools/qemu/build.yml

@@ -1 +0,0 @@
-image: qemu