build: unify kernel + system Docker builder (#27)

* unify

* add missing deps

* add findutils to alpine builder for GNU find -printf support

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* perl

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: greatgitsby

tools/build/Dockerfile.builder

@@ -1,15 +1,40 @@
-FROM ghcr.io/void-linux/void-glibc-full
+# check=error=true
 
-RUN xbps-install -yS
+FROM alpine:3.23.3
 
-RUN xbps-install -y \
-    base-devel \
+ARG UNAME
+ARG UID
+ARG GID
+
+RUN apk add --no-cache \
+    android-tools \
     bash \
+    bc \
+    bison \
+    build-base \
     ccache \
+    e2fsprogs \
+    findutils \
+    flex \
     git \
-    openssl-devel \
-    python3 && \
-    if [ "$(uname -m)" != "aarch64" ]; then xbps-install -y cross-aarch64-linux-gnu; fi && \
-    xbps-remove -O
+    libcap \
+    linux-headers \
+    openssl \
+    openssl-dev \
+    perl \
+    python3
+
+# Cross-compiler for x86_64 hosts building aarch64 kernel
+# gcc-aarch64-none-elf is bare-metal but works for kernel (freestanding code)
+RUN if [ "$(uname -m)" != "aarch64" ]; then \
+    apk add --no-cache gcc-aarch64-none-elf binutils-aarch64-none-elf; \
+    fi
+
+RUN if [ ${UID:-0} -ne 0 ] && [ ${GID:-0} -ne 0 ]; then \
+    deluser $(getent passwd ${UID} | cut -d : -f 1) > /dev/null 2>&1; \
+    delgroup $(getent group ${GID} | cut -d : -f 1) > /dev/null 2>&1; \
+    addgroup -g ${GID} ${UNAME} && \
+    adduser -u ${UID} -G ${UNAME} -D ${UNAME} \
+;fi
 
 ENTRYPOINT ["tail", "-f", "/dev/null"]

tools/build/Dockerfile.system-builder

@@ -22,7 +22,10 @@ fi
 # Build docker container
 echo "Building vamos-builder docker image"
 export DOCKER_BUILDKIT=1
-docker build -f tools/build/Dockerfile.builder -t vamos-builder "$DIR"
+docker build -f tools/build/Dockerfile.builder -t vamos-builder "$DIR" \
+  --build-arg UNAME="$(id -nu)" \
+  --build-arg UID="$(id -u)" \
+  --build-arg GID="$(id -g)"
 
 echo "Starting vamos-builder container"
 CONTAINER_ID=$(docker run -d -u "$(id -u):$(id -g)" -v "$DIR":"$DIR" -w "$DIR" vamos-builder)
@@ -54,7 +57,7 @@ build_kernel() {
   ARCH_HOST=$(uname -m)
   export ARCH=arm64
   if [ "$ARCH_HOST" != "aarch64" ] && [ "$ARCH_HOST" != "arm64" ]; then
-    export CROSS_COMPILE=aarch64-linux-gnu-
+    export CROSS_COMPILE=aarch64-none-elf-
   fi
 
   # ccache

tools/build/build_kernel.sh

@@ -49,14 +49,14 @@ export DOCKER_BUILDKIT=1
 docker buildx build -f tools/build/Dockerfile --check "$DIR"
 
 # Setup mount container for macOS and CI support
-echo "Building system-builder docker image"
-docker build -f tools/build/Dockerfile.system-builder -t vamos-system-builder "$DIR" \
+echo "Building vamos-builder docker image"
+docker build -f tools/build/Dockerfile.builder -t vamos-builder "$DIR" \
   --build-arg UNAME="$(id -nu)" \
   --build-arg UID="$(id -u)" \
   --build-arg GID="$(id -g)"
 
-echo "Starting system-builder container"
-MOUNT_CONTAINER_ID=$(docker run -d --privileged -v "$DIR:$DIR" vamos-system-builder)
+echo "Starting builder container"
+MOUNT_CONTAINER_ID=$(docker run -d --privileged -v "$DIR:$DIR" vamos-builder)
 
 # Cleanup containers on possible exit
 trap "echo \"Cleaning up containers:\"; \