Add build instructions

Signed-off-by: Knut Ahlers <knut@ahlers.me>

.gitignore

@@ -0,0 +1 @@
+.bin

Makefile

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+AVAIL_CMDS:=$(shell find . -mindepth 1 -name 'main.go' | cut -d '/' -f 2)
+
+default: clean $(patsubst %,.bin/%,$(AVAIL_CMDS))
+
+clean:
+	rm -rf .bin
+
+.bin/%: export CGO_ENABLED=0
+.bin/%:
+	cd $* && go build \
+		-trimpath \
+		-ldflags "-s -w -X main.version=$(shell git describe --tags --always || echo dev)" \
+		-o $(CURDIR)/.bin/$*