dockerfile based binary building

Using cross compilation toolchains that work from any platform
Adds darwin/arm64 support and bake targets. Static and dynamic
binary targets are available, both with glibc and musl.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

scripts/build/binary

@@ -1,14 +1,64 @@
-#!/usr/bin/env bash
+#!/usr/bin/env sh
 #
 # Build a static binary for the host OS/ARCH
 #
 
-set -eu -o pipefail
+set -eu
 
-source ./scripts/build/.variables
+: "${CGO_ENABLED=}"
+: "${GO_LINKMODE=static}"
+: "${GO_BUILDMODE=}"
+: "${GO_BUILDTAGS=}"
+: "${GO_STRIP=}"
 
-echo "Building statically linked $TARGET"
-export CGO_ENABLED=0
-go build -o "${TARGET}" --ldflags "${LDFLAGS}" "${SOURCE}"
+set -x
+. ./scripts/build/.variables
 
-ln -sf "$(basename "${TARGET}")" build/docker
+if [ -z "$CGO_ENABLED" ]; then
+    case "$(go env GOOS)" in
+        linux)
+            case "$(go env GOARCH)" in
+                amd64|arm64|arm|s390x)
+                    CGO_ENABLED=1
+                ;;
+                *)
+                    CGO_ENABLED=0
+                ;;
+            esac
+        ;;
+        darwin|windows)
+            CGO_ENABLED=1
+        ;;
+        *)
+            CGO_ENABLED=0
+        ;;
+    esac
+fi
+export CGO_ENABLED
+if [ "$CGO_ENABLED" = "1" ] && [ "$(go env GOOS)" != "windows" ]; then
+    case "$(go env GOARCH)" in
+        mips*|ppc64)
+            # pie build mode is not supported on mips architectures
+            ;;
+        *)
+            GO_BUILDMODE="-buildmode=pie"
+            ;;
+    esac
+    GO_BUILDTAGS="$GO_BUILDTAGS pkcs11"
+fi
+
+if [ "$CGO_ENABLED" = "1" ] && [ "$GO_LINKMODE" = "static" ] && [ "$(go env GOOS)" = "linux" ]; then
+    LDFLAGS="$LDFLAGS -extldflags -static"
+fi
+
+if [ -n "$GO_STRIP" ]; then
+    LDFLAGS="$LDFLAGS -s -w"
+fi
+
+echo "Building $GO_LINKMODE $(basename "${TARGET}")"
+
+export GO111MODULE=auto
+
+go build -o "${TARGET}" -tags "${GO_BUILDTAGS}" --ldflags "${LDFLAGS}" ${GO_BUILDMODE} "${SOURCE}"
+
+ln -sf "$(basename "${TARGET}")" "$(dirname "${TARGET}")/docker"