Pull request: all: update go and backend tools

Closes #2576.
Updates #2275.
Updates #2419.
Updates #2443.

Squashed commit of the following:

commit b1a4809ada298d675de12740051ba26fb9945957
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri May 21 14:01:40 2021 +0300

    all: add --local-frontend, upd docker

commit 619ee7c82f27e3405753003dbec556ffb056d025
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu May 20 15:02:33 2021 +0300

    bamboo-specs: bump docker version

commit 5c2b2fbce80afdcc81fd0cb83674dc3d64facbf1
Merge: 6536b32d 9c60aef6
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu May 20 15:01:47 2021 +0300

    Merge branch 'master' into 2275-upd-go

commit 6536b32dd4580425f7dedde6765463a79b9bd699
Merge: 9bb32bc4 6f7fd33a
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 19 20:38:48 2021 +0300

    Merge branch 'master' into 2275-upd-go

commit 9bb32bc4c0ac0f3a97195adc75359e48c9c58897
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 19 18:48:50 2021 +0300

    all: fix build, imp err handling

commit 6868eac7f7d2980fb706881f53e72afe5f7c3447
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 19 18:09:32 2021 +0300

    all: fix github lint

commit ebbb9c55f32fbd57e34e8b161016aa6b291c097c
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 19 17:36:56 2021 +0300

    all: update go and backend tools

scripts/make/Dockerfile

@@ -1,6 +1,6 @@
 # A docker file for scripts/make/build-docker.sh.
 
-FROM alpine:3.12
+FROM alpine:3.13
 
 ARG BUILD_DATE
 ARG VERSION

scripts/make/build-release.sh

@@ -153,6 +153,7 @@ readonly mipses
 #    os  arch      arm mips       snap
 platforms="\
 darwin   amd64     0   0          0
+darwin   arm64     0   0          0
 freebsd  386       0   0          0
 freebsd  amd64     0   0          0
 freebsd  arm       5   0          0

scripts/make/clean.sh

@@ -1,6 +1,7 @@
 #!/bin/sh
 
 verbose="${VERBOSE:-0}"
+readonly verbose
 
 if [ "$verbose" -gt '0' ]
 then
@@ -11,21 +12,19 @@ set -e -f -u
 
 dist_dir="$DIST_DIR"
 go="${GO:-go}"
+sudo_cmd="${SUDO:-}"
+readonly dist_dir go sudo_cmd
 
-# Set the GOPATH explicitly in case make clean is called from under sudo after
-# a Docker build.
-env PATH="$( "$go" env GOPATH )/bin":"$PATH" packr clean
-
-rm -f\
+$sudo_cmd rm -f\
 	./AdGuardHome\
 	./AdGuardHome.exe\
 	./coverage.txt\
 	;
 
-rm -f -r\
+$sudo_cmd rm -f -r\
 	./bin/\
-	./build/\
-	./build2/\
+	./build/static/\
+	./build2/static/\
 	./client/node_modules/\
 	./client2/node_modules/\
 	./data/\

scripts/make/go-deps.sh

@@ -7,34 +7,22 @@ if [ "$verbose" -gt '1' ]
 then
 	env
 	set -x
-	v_flags='-v'
 	x_flags='-x'
 elif [ "$verbose" -gt '0' ]
 then
 	set -x
-	v_flags='-v'
 	x_flags=''
 else
 	set +x
-	v_flags=''
 	x_flags=''
 fi
-readonly v_flags x_flags
+readonly x_flags
 
 set -e -f -u
 
 go="${GO:-go}"
+readonly go
 
 # Don't use quotes with flag variables because we want an empty space if those
 # aren't set.
 "$go" mod download $x_flags
-
-# Reset GOARCH and GOOS to make sure we install the tools for the native
-# architecture even when we're cross-compiling the main binary, and also to
-# prevent the "cannot install cross-compiled binaries when GOBIN is set" error.
-env\
-	GOARCH=""\
-	GOOS=""\
-	GOBIN="${PWD}/bin"\
-	"$go" install $v_flags $x_flags\
-	github.com/gobuffalo/packr/packr

scripts/make/go-lint.sh

@@ -49,7 +49,7 @@ trap not_found EXIT
 
 # Warnings
 
-go_min_version='go1.15'
+go_min_version='go1.16'
 go_min_version_prefix="go version ${go_min_version}"
 go_version_msg="
 warning: your go version is different from the recommended minimal one (${go_min_version}).
@@ -74,11 +74,11 @@ esac
 
 # Simple Analyzers
 
-# blocklist_imports is a simple check against unwanted packages.  Currently it
-# only looks for package log which is replaced by our own package
+# blocklist_imports is a simple check against unwanted packages.  Package
+# io/ioutil is soft-deprecated.  Package log is replaced by our own package
 # github.com/AdguardTeam/golibs/log.
 blocklist_imports() {
-	git grep -F -e '"log"' -- '*.go' || exit 0;
+	git grep -F -e '"io/ioutil"' -e '"log"' -- '*.go' || exit 0;
 }
 
 # method_const is a simple check against the usage of some raw strings and
@@ -154,7 +154,7 @@ exit_on_output() (
 
 # Constants
 
-go_files='./main.go ./tools.go ./internal/'
+go_files='./main.go ./internal/'
 readonly go_files