chore: enable riscv64 build

Signed-off-by: CrazyMax <[email protected]>
(cherry picked from commit cc7b649)

Author: crazy-max

.github/workflows/buildkit.yml

@@ -25,7 +25,7 @@ env:
   SETUP_BUILDX_VERSION: "latest"
   SETUP_BUILDKIT_IMAGE: "moby/buildkit:latest"
   IMAGE_NAME: "moby/buildkit"
-  PLATFORMS: "linux/amd64,linux/arm/v7,linux/arm64,linux/s390x,linux/ppc64le"
+  PLATFORMS: "linux/amd64,linux/arm/v7,linux/arm64,linux/s390x,linux/ppc64le,linux/riscv64"
   DESTDIR: "./bin"
 
 jobs:

.github/workflows/frontend.yml

@@ -23,7 +23,7 @@ env:
   SETUP_BUILDX_VERSION: "latest"
   SETUP_BUILDKIT_TAG: "moby/buildkit:latest"
   IMAGE_NAME: "docker/dockerfile-upstream"
-  PLATFORMS: "linux/386,linux/amd64,linux/arm/v7,linux/arm64,linux/mips,linux/mipsle,linux/mips64,linux/mips64le,linux/s390x,linux/ppc64le"
+  PLATFORMS: "linux/386,linux/amd64,linux/arm/v7,linux/arm64,linux/mips,linux/mipsle,linux/mips64,linux/mips64le,linux/s390x,linux/ppc64le,linux/riscv64"
 
 jobs:
   test:

docker-bake.hcl

@@ -56,8 +56,7 @@ target "binaries-cross" {
     "linux/arm64",
     "linux/s390x",
     "linux/ppc64le",
-    # TODO: enable back once https://github.com/moby/buildkit/issues/4316 is fixed
-    // "linux/riscv64",
+    "linux/riscv64",
     "windows/amd64",
     "windows/arm64"
   ]