Merge #17011: ci: Use busybox utils for one build

ddddd8961b6209cba1bcabad73916051a99f2025 ci: Use busybox utils for one build (MarcoFalke)

Pull request description:

  To make sure Bitcoin Core can be built with BusyBox, see https://github.com/bitcoin/bitcoin/pull/16927#issuecomment-536483706

ACKs for top commit:
  laanwj:
    ACK ddddd8961b6209cba1bcabad73916051a99f2025

Tree-SHA512: da3a4654ee7975206d04643675d309b4973a510ca344acaec97fb1ed19c43cf13489bdf236c92c4a90499ec5b3c18c3338fff096110b26abee5ffe955089f267

3 files changed, 18 insertions, 4 deletions

diff --git a/ci/test/00_setup_env.sh b/ci/test/00_setup_env.sh
index 94598835ac..8bc50da2c3 100755
--- a/ci/test/00_setup_env.sh
+++ b/ci/test/00_setup_env.sh
@@ -22,6 +22,8 @@ export MAKEJOBS=${MAKEJOBS:--j4}
 # A folder for the ci system to put temporary files (ccache, datadirs for tests, ...)
 export BASE_SCRATCH_DIR=${BASE_SCRATCH_DIR:-$BASE_ROOT_DIR/ci/scratch/}
 export HOST=${HOST:-x86_64-unknown-linux-gnu}
+# Whether to prefer BusyBox over GNU utilities
+export USE_BUSY_BOX=${USE_BUSY_BOX:-false}
 export RUN_UNIT_TESTS=${RUN_UNIT_TESTS:-true}
 export RUN_FUNCTIONAL_TESTS=${RUN_FUNCTIONAL_TESTS:-true}
 export RUN_FUZZ_TESTS=${RUN_FUZZ_TESTS:-false}
diff --git a/ci/test/00_setup_env_arm.sh b/ci/test/00_setup_env_arm.sh
index ac7ace8c3b..db640015b1 100644
--- a/ci/test/00_setup_env_arm.sh
+++ b/ci/test/00_setup_env_arm.sh
@@ -7,7 +7,8 @@
 export LC_ALL=C.UTF-8
 
 export HOST=arm-linux-gnueabihf
-export PACKAGES="python3 g++-arm-linux-gnueabihf"
+export PACKAGES="python3 g++-arm-linux-gnueabihf busybox"
+export USE_BUSY_BOX=true
 export RUN_UNIT_TESTS=false
 export RUN_FUNCTIONAL_TESTS=false
 export GOAL="install"
diff --git a/ci/test/04_install.sh b/ci/test/04_install.sh
index 4459d6f4ce..409e87ce04 100755
--- a/ci/test/04_install.sh
+++ b/ci/test/04_install.sh
@@ -33,18 +33,29 @@ if [ -z "$RUN_CI_ON_HOST" ]; then
   DOCKER_ID=$(docker run $DOCKER_ADMIN -idt --mount type=bind,src=$BASE_BUILD_DIR,dst=$BASE_BUILD_DIR --mount type=bind,src=$CCACHE_DIR,dst=$CCACHE_DIR -w $BASE_BUILD_DIR --env-file /tmp/env $DOCKER_NAME_TAG)
 
   DOCKER_EXEC () {
-    docker exec $DOCKER_ID bash -c "cd $PWD && $*"
+    docker exec $DOCKER_ID bash -c "export PATH=$BASE_SCRATCH_DIR/bins/:\$PATH && cd $PWD && $*"
   }
 else
   echo "Running on host system without docker wrapper"
   DOCKER_EXEC () {
-    bash -c "cd $PWD && $*"
+    bash -c "export PATH=$BASE_SCRATCH_DIR/bins/:\$PATH && cd $PWD && $*"
   }
 fi
 
 DOCKER_EXEC free -m -h
-DOCKER_EXEC echo "Number of CPUs \(nproc\): $(nproc)"
+DOCKER_EXEC echo "Number of CPUs \(nproc\):" \$\(nproc\)
 
 ${CI_RETRY_EXE} DOCKER_EXEC apt-get update
 ${CI_RETRY_EXE} DOCKER_EXEC apt-get install --no-install-recommends --no-upgrade -y $PACKAGES $DOCKER_PACKAGES
 
+if [ "$USE_BUSY_BOX" = "true" ]; then
+  echo "Setup to use BusyBox utils"
+  DOCKER_EXEC mkdir -p $BASE_SCRATCH_DIR/bins/
+  # tar excluded for now because it requires passing in the exact archive type in ./depends (fixed in later BusyBox version)
+  # find excluded for now because it does not recognize the -delete option in ./depends (fixed in later BusyBox version)
+  # ar excluded for now because it does not recognize the -q option in ./depends (unknown if fixed)
+  # shellcheck disable=SC1010
+  DOCKER_EXEC for util in \$\(busybox --list \| grep -v "^ar$" \| grep -v "^tar$" \| grep -v "^find$"\)\; do ln -s \$\(command -v busybox\) $BASE_SCRATCH_DIR/bins/\$util\; done
+  # Print BusyBox version
+  DOCKER_EXEC patch --help
+fi