build: target for docker building

Adapted from #384.

Thanks @cas.

Makefile

@@ -2,6 +2,7 @@ ABRA         := ./cmd/abra
 KADABRA      := ./cmd/kadabra
 COMMIT       := $(shell git rev-list -1 HEAD)
 GOPATH       := $(shell go env GOPATH)
+GOVERSION    := 1.21
 LDFLAGS      := "-X 'main.Commit=$(COMMIT)'"
 DIST_LDFLAGS := $(LDFLAGS)" -s -w"
 
@@ -30,6 +31,13 @@ build-kadabra:
 
 build: build-abra build-kadabra
 
+build-docker-abra:
+	@docker run -it \
+		-v $(PWD):/abra golang:$(GOVERSION) \
+		bash -c 'cd /abra; mv scripts/docker/build.sh .; ./build.sh'
+
+build-docker: build-docker-abra
+
 clean:
 	@rm '$(GOPATH)/bin/abra'
 	@rm '$(GOPATH)/bin/kadabra'

build.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+if [ ! -f .envrc ]; then
+    . .envrc.sample
+else
+    . .envrc
+fi
+
+git config --global --add safe.directory /abra  # work around funky file permissions
+
+make build