patch, 4 partsAdd a CI for unsigned char system

diff --git a/ci/lib.sh b/ci/lib.sh
index db7105e8a8..661076e70b 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -227,11 +227,6 @@ export SKIP_DASHED_BUILT_INS=YesPlease
 
 case "$runs_on_pool" in
 ubuntu-*)
-	if test "$jobname" = "linux-gcc-default"
-	then
-		break
-	fi
-
 	PYTHON_PACKAGE=python2
 	if test "$jobname" = linux-gcc
 	then

diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 4f407530d3..9a32af8968 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -6,16 +6,12 @@
 . ${0%/*}/lib.sh
 
 P4WHENCE=https://cdist2.perforce.com/perforce/r21.2
-LFSWHENCE=https://github.com/github/git-lfs/releases/download/v$LINUX_GIT_LFS_VERSION
+LFSWHENCE=https://github.com/github/git-lfs/releases/download
 UBUNTU_COMMON_PKGS="make libssl-dev libcurl4-openssl-dev libexpat-dev
  tcl tk gettext zlib1g-dev perl-modules liberror-perl libauthen-sasl-perl
  libemail-valid-perl libio-socket-ssl-perl libnet-smtp-ssl-perl"
 
-case "$runs_on_pool" in
-ubuntu-*)
-	sudo apt-get -q update
-	sudo apt-get -q -y install language-pack-is libsvn-perl apache2 \
-		$UBUNTU_COMMON_PKGS $CC_PACKAGE $PYTHON_PACKAGE
+_install_linux_p4() {
 	mkdir --parents "$P4_PATH"
 	pushd "$P4_PATH"
 		wget --quiet "$P4WHENCE/bin.linux26x86_64/p4d"
@@ -23,12 +19,36 @@ ubuntu-*)
 		chmod u+x p4d
 		chmod u+x p4
 	popd
+}
+
+_install_linux_git_lfs() {
+	local whence fname
+	whence="$1"
+	fname="$2"
 	mkdir --parents "$GIT_LFS_PATH"
 	pushd "$GIT_LFS_PATH"
-		wget --quiet "$LFSWHENCE/git-lfs-linux-amd64-$LINUX_GIT_LFS_VERSION.tar.gz"
-		tar --extract --gunzip --file "git-lfs-linux-amd64-$LINUX_GIT_LFS_VERSION.tar.gz"
-		cp git-lfs-$LINUX_GIT_LFS_VERSION/git-lfs .
+		wget --quiet "$whence/$fname"
+		tar --extract --gunzip --strip-components=1 --file "$fname"
 	popd
+}
+
+case "$runs_on_pool" in
+ubuntu-*)
+	sudo apt-get -q update
+	sudo apt-get -q -y install language-pack-is libsvn-perl apache2 \
+		$UBUNTU_COMMON_PKGS $CC_PACKAGE $PYTHON_PACKAGE
+
+	case "$(uname -m)" in
+	x86_64)
+		_install_linux_p4
+		_install_linux_git_lfs "$LFSWHENCE/v${LINUX_GIT_LFS_VERSION}" \
+			"git-lfs-linux-amd64-$LINUX_GIT_LFS_VERSION.tar.gz"
+		;;
+	*)
+		echo "Not supported architecture" >&2
+		exit 1
+		;;
+	esac
 	;;
 macos-*)
 	export HOMEBREW_NO_AUTO_UPDATE=1 HOMEBREW_NO_INSTALL_CLEANUP=1

ci/install-dependencies.sh, ci/lib.sh

diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 9a32af8968..6d587ffc54 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -44,6 +44,10 @@ ubuntu-*)
 		_install_linux_git_lfs "$LFSWHENCE/v${LINUX_GIT_LFS_VERSION}" \
 			"git-lfs-linux-amd64-$LINUX_GIT_LFS_VERSION.tar.gz"
 		;;
+	aarch64)
+		_install_linux_git_lfs "$LFSWHENCE/v${LINUX_GIT_LFS_VERSION}" \
+			"git-lfs-linux-arm64-v$LINUX_GIT_LFS_VERSION.tar.gz"
+		;;
 	*)
 		echo "Not supported architecture" >&2
 		exit 1
diff --git a/ci/lib.sh b/ci/lib.sh
index 661076e70b..3c19267a56 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -242,6 +242,12 @@ ubuntu-*)
 	# image.
 	# Keep that in mind when you encounter a broken OS X build!
 	export LINUX_GIT_LFS_VERSION="1.5.2"
+	# The Linux arm64 build installs yet another recent version, since
+	# above version doesn't ship prebuilt binaries for arm64.
+	if test "$(uname -m)" = aarch64
+	then
+		LINUX_GIT_LFS_VERSION="3.3.0"
+	fi
 
 	P4_PATH="$HOME/custom/p4"
 	GIT_LFS_PATH="$HOME/custom/git-lfs"

.circleci/config.yml, ci/lib.sh

diff --git a/.circleci/config.yml b/.circleci/config.yml
new file mode 100644
index 0000000000..2f5e0966b7
--- /dev/null
+++ b/.circleci/config.yml
@@ -0,0 +1,17 @@
+# .circleci/config.yml
+jobs:
+  build:
+    machine:
+      image: ubuntu-2004:2022.04.1
+    resource_class: arm.medium
+    environment:
+      jobname: linux-gcc
+      runs_on_pool: ubuntu-arm64
+    steps:
+    - checkout
+    - run: ci/install-dependencies.sh
+    - run:
+        name: Build and Tests
+        command: ci/run-build-and-tests.sh
+    - store_test_results:
+        path: t/out
diff --git a/ci/lib.sh b/ci/lib.sh
index 3c19267a56..8b0c727950 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -201,6 +201,25 @@ then
 	MAKEFLAGS="$MAKEFLAGS --jobs=10"
 	test windows != "$CI_OS_NAME" ||
 	GIT_TEST_OPTS="--no-chain-lint --no-bin-wrappers $GIT_TEST_OPTS"
+elif test "$CIRCLECI" = true
+then
+	CI_TYPE=circleci
+	CI_BRANCH="$CIRCLE_BRANCH"
+	CI_COMMIT="$CIRCLE_SHA1"
+	CI_JOB_ID="$CIRCLE_WORKFLOW_JOB_ID"
+	CI_JOB_NUMBER="$CIRCLE_BUILD_NUM"
+	CI_OS_NAME="$(echo "$AGENT_OS" | tr A-Z a-z)"
+	test darwin != "$CI_OS_NAME" || CI_OS_NAME=osx
+	CI_REPO_SLUG="$(expr "$CIRCLE_REPOSITORY_URL" : '.*:\([^/]*/[^/]*\)\.git$')"
+	CC="${CC:-gcc}"
+
+	# use a subdirectory of the cache dir (because the file share is shared
+	# among *all* phases)
+	cache_dir="$HOME/none"
+
+	export GIT_PROVE_OPTS="--timer --jobs 10"
+	export GIT_TEST_OPTS="--verbose-log -x --write-junit-xml"
+	MAKEFLAGS="$MAKEFLAGS --jobs=10"
 else
 	echo "Could not identify CI type" >&2
 	env >&2