disable cgo, build PIE when possible

closes #26

Makefile

@@ -2,7 +2,7 @@ NAME := gdu
 PACKAGE := github.com/dundee/$(NAME)
 VERSION := $(shell git describe --tags)
 GOFLAGS ?= -buildmode=pie -trimpath -mod=readonly -modcacherw
-LDFLAGS := "-s -w \
+LDFLAGS := "-s -w -extldflags '-static' \
 	-X '$(PACKAGE)/build.Version=$(VERSION)' \
 	-X '$(PACKAGE)/build.User=$(shell id -u -n)' \
 	-X '$(PACKAGE)/build.Time=$(shell LC_ALL=en_US.UTF-8 date)'"
@@ -13,26 +13,28 @@ run:
 build:
 	@echo "Version: " $(VERSION)
 	mkdir -p dist
-	GOFLAGS="$(GOFLAGS)" go build -ldflags=$(LDFLAGS) -o dist/$(NAME) .
+	GOFLAGS="$(GOFLAGS)" CGO_ENABLED=0 go build -a -ldflags=$(LDFLAGS) -o dist/$(NAME) .
 
 build-all:
 	@echo "Version: " $(VERSION)
 	-mkdir dist
-	-gox \
+	-CGO_ENABLED=0 gox \
 		-os="darwin windows" \
 		-arch="amd64" \
 		-output="dist/{{.Dir}}_{{.OS}}_{{.Arch}}" \
 		-ldflags=$(LDFLAGS)
 
-	-gox \
+	-CGO_ENABLED=0 gox \
 		-os="linux freebsd netbsd openbsd" \
 		-output="dist/{{.Dir}}_{{.OS}}_{{.Arch}}" \
 		-ldflags=$(LDFLAGS)
 
-	cd dist; GOOS=linux GOARM=5 GOARCH=arm go build -ldflags=$(LDFLAGS) -o gdu_linux_armv5l ..
-	cd dist; GOOS=linux GOARM=6 GOARCH=arm go build -ldflags=$(LDFLAGS) -o gdu_linux_armv6l ..
-	cd dist; GOOS=linux GOARM=7 GOARCH=arm go build -ldflags=$(LDFLAGS) -o gdu_linux_armv7l ..
-	cd dist; GOOS=linux GOARCH=arm64 go build -ldflags=$(LDFLAGS) -o gdu_linux_arm64 ..
+	cd dist; GOFLAGS="$(GOFLAGS)" CGO_ENABLED=0 go build -a -ldflags=$(LDFLAGS) -o gdu_linux_amd64 ..
+
+	cd dist; CGO_ENABLED=0 GOOS=linux GOARM=5 GOARCH=arm go build -ldflags=$(LDFLAGS) -o gdu_linux_armv5l ..
+	cd dist; CGO_ENABLED=0 GOOS=linux GOARM=6 GOARCH=arm go build -ldflags=$(LDFLAGS) -o gdu_linux_armv6l ..
+	cd dist; CGO_ENABLED=0 GOOS=linux GOARM=7 GOARCH=arm go build -ldflags=$(LDFLAGS) -o gdu_linux_armv7l ..
+	cd dist; CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build -ldflags=$(LDFLAGS) -o gdu_linux_arm64 ..
 
 	cd dist; for file in gdu_linux_* gdu_darwin_* gdu_netbsd_* gdu_openbsd_* gdu_freebsd_*; do tar czf $$file.tgz $$file; done
 	cd dist; for file in gdu_windows_*; do zip $$file.zip $$file; done