make build-release.sh works on Mac OSX

Dockerfile

@@ -2,7 +2,7 @@ FROM golang:1.13-alpine as builder
 WORKDIR $GOPATH/src/github.com/loadimpact/k6
 ADD . .
 RUN apk --no-cache add git
-RUN CGO_ENABLED=0 go install -a -ldflags "-s -w -X github.com/loadimpact/k6/lib/consts.VersionDetails=$(date --utc -Is)/$(git describe --always --long --dirty)"
+RUN CGO_ENABLED=0 go install -a -ldflags "-s -w -X github.com/loadimpact/k6/lib/consts.VersionDetails=$(date -u +"%FT%T%z")/$(git describe --always --long --dirty)"
 
 FROM alpine:3.10
 RUN apk add --no-cache ca-certificates

build-release.sh

@@ -8,7 +8,7 @@ eval "$(go env)"
 VERSION=${1:-$(git describe --tags --always --dirty)}
 
 # To overwrite the version details, pass something as the second arg. Empty string disables it.
-VERSION_DETAILS=${2-"$(date --utc --iso-8601=s)/$(git describe --always --long --dirty)"}
+VERSION_DETAILS=${2-"$(date -u +"%FT%T%z")/$(git describe --always --long --dirty)"}
 
 make_archive() {
 	local FMT="$1" DIR="$2"
@@ -39,6 +39,7 @@ build_dist() {
 	# Clean out any old remnants of failed builds.
 	rm -rf "dist/$DIR"
 	mkdir -p "dist/$DIR"
+	trap "rm -rf \"dist/$DIR\"" INT TERM
 
 	# Subshell to not mess with the current env vars or CWD
 	(
@@ -60,16 +61,16 @@ checksum() {
 	local CHECKSUM_FILE="k6-${VERSION}-checksums.txt"
 
 	if command -v sha256sum > /dev/null; then
-		CHECKSUM_CMD="sha256sum"
+		CHECKSUM_CMD=("sha256sum")
 	elif command -v shasum > /dev/null; then
-		CHECKSUM_CMD="shasum -a 256"
+		CHECKSUM_CMD=("shasum" "-a" "256")
 	else
 		echo "ERROR: unable to find a command to compute sha-256 hash"
 		return 1
 	fi
 
 	rm -f "dist/$CHECKSUM_FILE"
-	( cd dist && for x in *; do "$CHECKSUM_CMD" "$x" >> "$CHECKSUM_FILE"; done )
+	( cd dist && for x in *; do "${CHECKSUM_CMD[@]}" -- "$x" >> "$CHECKSUM_FILE"; done )
 }
 
 echo "--- Building Release: ${VERSION}"