Add src bake target to retrieve the qemu source with patches applied

Signed-off-by: Tibor Vass <[email protected]>

Dockerfile

@@ -11,13 +11,13 @@ ARG QEMU_REPO=https://github.com/qemu/qemu
 # xx is a helper for cross-compilation
 FROM --platform=$BUILDPLATFORM tonistiigi/xx@sha256:56b19a5fb89b99195ec494d59ad34370d14540858c1f56c560ec1e7f2d1c177f AS xx
 
-FROM --platform=$BUILDPLATFORM ${ALPINE_BASE} AS src
+FROM --platform=$BUILDPLATFORM ${ALPINE_BASE} AS src-clone
 RUN apk add --no-cache git patch
 
 WORKDIR /src
 ARG QEMU_VERSION
 ARG QEMU_REPO
-RUN git clone $QEMU_REPO && cd qemu && git checkout $QEMU_VERSION
+RUN mkdir qemu && cd qemu && git init && git fetch --depth 1 $QEMU_REPO $QEMU_VERSION && git checkout FETCH_HEAD
 COPY patches patches
 ARG QEMU_PATCHES=cpu-max
 ARG QEMU_PATCHES_ALL=${QEMU_PATCHES},alpine-patches,zero-init-msghdr,sched
@@ -53,6 +53,9 @@ RUN <<eof
   scripts/git-submodule.sh update ui/keycodemapdb tests/fp/berkeley-testfloat-3 tests/fp/berkeley-softfloat-3 dtc slirp
 eof
 
+FROM scratch AS src
+COPY --from=src-clone /src/qemu/ /
+
 FROM --platform=$BUILDPLATFORM ${ALPINE_BASE} AS base
 RUN apk add --no-cache git clang lld python3 llvm make ninja pkgconfig glib-dev gcc musl-dev perl bash
 COPY --from=xx / /
@@ -70,7 +73,7 @@ FROM base AS build
 ARG TARGETPLATFORM
 ARG QEMU_VERSION QEMU_TARGETS
 ENV AR=llvm-ar STRIP=llvm-strip
-RUN --mount=target=.,from=src,src=/src/qemu,rw --mount=target=./install-scripts,src=scripts \
+RUN --mount=target=.,from=src-clone,src=/src/qemu,rw --mount=target=./install-scripts,src=scripts \
   TARGETPLATFORM=${TARGETPLATFORM} configure_qemu.sh && \
   make -j "$(getconf _NPROCESSORS_ONLN)" && \
   make install && \

docker-bake.hcl

@@ -7,6 +7,9 @@ variable "QEMU_REPO" {
 variable "QEMU_VERSION" {
   default = "v6.2.0"
 }
+variable "QEMU_PATCHES" {
+  default = "cpu-max,buildkit-direct-execve-v6.2"
+}
 
 // Special target: https://github.com/docker/metadata-action#bake-definition
 target "meta-helper" {
@@ -54,7 +57,7 @@ target "buildkit" {
   inherits = ["mainline"]
   args = {
     BINARY_PREFIX = "buildkit-"
-    QEMU_PATCHES = "cpu-max,buildkit-direct-execve-v6.2"
+    QEMU_PATCHES = QEMU_PATCHES
     QEMU_PRESERVE_ARGV0 = ""
   }
   cache-from = ["${REPO}:buildkit-master"]
@@ -80,4 +83,14 @@ target "archive" {
 
 target "archive-all" {
   inherits = ["archive", "all-arch"]
-}
+}
+
+target "src" {
+  inherits = ["mainline"]
+  args = {
+    QEMU_PATCHES = QEMU_PATCHES
+    QEMU_PRESERVE_ARGV0 = ""
+  }
+  target = "src"
+  output = ["./qemu"]
+}