refactor: replace ./make (python3) with ./mk (makefile) (#343)

This pull request fixes https://github.com/ooni/probe/issues/1471. We have replaced the original build script (`./make`) with the `./mk` makefile (executable using `#!/usr/bin/make -f`). We concluded supporting direct builds from Windows is not worth the effort and halving the code we need to maintain is probably a good plus. Both macOS and Linux install GNU make at `/usr/bin/make`, so we should be okay in the common use cases.

I significantly simplified the management of Go versioning by requiring the user to manage it and by enforcing that we are using the desired Go version. This speeds up builds and works in sane operating systems that use the last version of a specific package. Otherwise, it's possible to use the `go get golang.org/dl/go${version}` feature.

The remaining question mark was related to updating the Android SDK. I have determined that a good course of action is pinning to the latest CLI tools and always forcing the CLI tools to install the latest required packages (e.g., the NDK).

CLI/linux/build

@@ -1,15 +1,18 @@
 #!/bin/sh
-# This script is executed by `./make` when building inside
+# This script is executed by `./mk` when building inside
 # an Alpine Linux docker container. Using Alpine Linux, which
 # uses musl libc, allows us to emit static binaries.
 set -e
 if [ "$GOARCH" = "" ]; then
-    echo 'fatal: $GOARCH is not set' 1>&2
-    exit 1
+	echo 'fatal: GOARCH is not set' 1>&2
+	exit 1
 fi
 set -x
 apk update
 apk upgrade
 apk add --no-progress gcc git linux-headers musl-dev
-CGO_ENABLED=1 GOOS=linux GOARCH=$GOARCH go build -o ./CLI/linux/$GOARCH/ \
-    -ldflags='-s -w -extldflags "-static"' "$@" ./cmd/ooniprobe
+export GOPATH=$GOPATH
+export CGO_ENABLED=1
+export GOOS=linux
+export GOARCH=$GOARCH
+go build -o "./CLI/linux/$GOARCH/" -ldflags='-s -w -extldflags "-static"' "$@" ./cmd/ooniprobe

CLI/linux/debian

@@ -1,5 +1,5 @@
 #!/bin/sh
-# This script creates a Debian package. When run by `./make`, it
+# This script creates a Debian package. When run by `./mk`, it
 # is run inside a debian:stable container. It's fine to also
 # run this script from any debian-like system, as long as the
 # following ASSUMPTIONS are met:
@@ -11,8 +11,8 @@
 # architecture of the `ooniprobe` we are packaging.
 
 if [ $# -gt 1 ]; then
-    echo "usage: $0 [run_number]" 1>&2
-    exit 1
+	echo "usage: $0 [run_number]" 1>&2
+	exit 1
 fi
 run_number=$1
 
@@ -20,32 +20,32 @@ run_number=$1
 # by the debian/ooniprobe-cli.install file.
 rm -rf ./debian/bin
 mkdir -p ./debian/bin
-machine=`uname -m`
+machine=$(uname -m)
 goarch=""
 case $machine in
-    x86_64)
-        cp ./CLI/linux/amd64/ooniprobe ./debian/bin
-        goarch=amd64
-    ;;
-    aarch64)
-        cp ./CLI/linux/arm64/ooniprobe ./debian/bin
-        goarch=arm64
-    ;;
-    *)
-        # TODO(bassosimone): here we probably want to further extend
-        # this script to support at least armv7.
-        echo "FATAL: unsupported machine: $machine" 1>&2
-        exit 1
-    ;;
+x86_64)
+	cp ./CLI/linux/amd64/ooniprobe ./debian/bin
+	goarch=amd64
+	;;
+aarch64)
+	cp ./CLI/linux/arm64/ooniprobe ./debian/bin
+	goarch=arm64
+	;;
+*)
+	# TODO(bassosimone): here we probably want to further extend
+	# this script to support at least armv7.
+	echo "FATAL: unsupported machine: $machine" 1>&2
+	exit 1
+	;;
 esac
 
 set -ex
 
 # figure out the version number from the binary itself (which rests
-# on the assumption that `uname -m` can run such a binary)
-version=`./debian/bin/ooniprobe version`
-if [ ! -z $run_number ]; then
-    version="${version}~${run_number}"
+# on the assumption that we can run such a binary)
+version=$(./debian/bin/ooniprobe version)
+if [ -n "$run_number" ]; then
+	version="${version}~${run_number}"
 fi
 
 # The OONI_DEB_DRY_RUN is a semi-undocumented feature allowing
@@ -58,7 +58,7 @@ $OONI_DEB_DRY_RUN apt-get build-dep -y --no-install-recommends .
 # keep the original changelog file safe
 $OONI_DEB_DRY_RUN cp ./debian/changelog ./debian/changelog.oocopy
 
-$OONI_DEB_DRY_RUN dch -v $version "New version ${version}"
+$OONI_DEB_DRY_RUN dch -v "$version" "New version ${version}"
 $OONI_DEB_DRY_RUN dpkg-buildpackage -us -uc -b
 
 # restore the original changelog file
@@ -70,4 +70,4 @@ $OONI_DEB_DRY_RUN mv ../*.deb .
 
 # install the package on the container as a smoke test to
 # ensure that it is installable.
-DEBIAN_FRONTEND=noninteractive dpkg -i ooniprobe-cli_${version}_${goarch}.deb
+DEBIAN_FRONTEND=noninteractive dpkg -i "ooniprobe-cli_${version}_${goarch}.deb"