remove unused emulators from exported image

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

Author: tonistiigi

Dockerfile

@@ -161,10 +161,15 @@ COPY --link --from=cni-plugins /opt/cni/bin/firewall /buildkit-cni-firewall
 FROM scratch AS cni-plugins-export-squashed
 COPY --from=cni-plugins-export / /
 
+FROM --platform=$BUILDPLATFORM alpine:${ALPINE_VERSION} AS binfmt-filter
+# built from https://github.com/tonistiigi/binfmt/releases/tag/buildkit%2Fv9.2.0-50
+COPY --link --from=tonistiigi/binfmt:buildkit-v9.2.0-50@sha256:ff21b00e7238dce3bbd74fbe25591f7213837a77861b47b2df5e019540ec33fa / /out/
+WORKDIR /out/
+RUN rm buildkit-qemu-loongarch64 buildkit-qemu-mips64 buildkit-qemu-mips64el
+
 FROM scratch AS binaries-linux
 COPY --link --from=runc /usr/bin/runc /buildkit-runc
-# built from https://github.com/tonistiigi/binfmt/releases/tag/buildkit%2Fv9.2.0-50
-COPY --link --from=tonistiigi/binfmt:buildkit-v9.2.0-50@sha256:ff21b00e7238dce3bbd74fbe25591f7213837a77861b47b2df5e019540ec33fa / /
+COPY --link --from=binfmt-filter /out/ /
 COPY --link --from=cni-plugins-export-squashed / /
 COPY --link --from=buildctl /usr/bin/buildctl /
 COPY --link --from=buildkitd /usr/bin/buildkitd /

solver/llbsolver/ops/exec_binfmt.go

@@ -27,7 +27,6 @@ var qemuArchMap = map[string]string{
 	"riscv64": "riscv64",
 	"arm":     "arm",
 	"s390x":   "s390x",
-	"ppc64":   "ppc64",
 	"ppc64le": "ppc64le",
 	"386":     "i386",
 }