Add darwin_arm64 build using docker

.travis.yml

@@ -8,9 +8,20 @@ script:
   - CGO_ENABLED=0 GOOS=linux GOARCH=arm GOARM=6 go build -o "mkcert-$(git describe --tags)-linux-arm"
         -ldflags "-X main.Version=$(git describe --tags)"
   - CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 go build -o "mkcert-$(git describe --tags)-darwin-amd64"
-        -ldflags "-X main.Version=$(git describe --tags)"
+       -ldflags "-X main.Version=$(git describe --tags)"
   - CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build -o "mkcert-$(git describe --tags)-windows-amd64.exe"
         -ldflags "-X main.Version=$(git describe --tags)"
+  # TODO: When golang v1.16 comes out, make this a simple build using go instead of gotip (lose docker)
+  - docker run --rm -w /workdir -v "$(PWD):/workdir" -e GOPATH="/go" -e "GOCACHE=/workdir/.gotmp"  drud/golang-build-container:v1.15.6 bash -c "CGO_ENABLED=0 GOOS=darwin GOARCH=arm64 gotip build -o \"mkcert-$(git describe --tags)-darwin-arm64\" -ldflags \"-X main.Version=$(git describe --tags)\" "
+
+  DOCKERBUILDCMD=docker run -t --rm                     \
+  -v "/$(PWD)://workdir$(DOCKERMOUNTFLAG)"                              \
+  -e GOPATH="//workdir/$(GOTMP)" \
+  -e GOCACHE="//workdir/$(GOTMP)/.cache" \
+  -e GOFLAGS="$(USEMODVENDOR)" \
+  -e CGO_ENABLED=0 \
+  -w //workdir              \
+  $(BUILD_IMAGE)
 
 deploy:
   provider: releases
@@ -20,5 +31,5 @@ deploy:
   api_key:
     secure: "Vd1M3TelYxwpWDe7qawK23LvSttF6xuOjwz9BQOlevidONDx/Wf2JwM8ggSt/mlvYp/FH57PX2TOWqTnVD0Hkt7Ds7CPyLSRwpgQdB8qqYBIuGBmWRXSoHc46qauWiSEJiGOO1/aqfwdROQlu/JvQyNEzzZsLsmqDIqwIOdYcauq3tYjkL48VKensGg0d8JcLuCZ+niXMOYrJa/3EdQFAij1ZlwYZt76dS/XcZ2BKhGexPOrgUaMyl9GOsd7fft71hS0aN4xDHbut5psbe1MJaGan0DUWBiCXLNjFwgFPtEHes3ddq98VVCv7iSDvO2E2nQuwoAS+pQgpPHNpiOzoomdbr/d5OGW2s2xy8tozjoQTUfUQ0wkfTG4YzFKj66xZ4Ut8+/LdN5TZvPITqQqyXJ3a3u0KSivOkjH6M+BtTQjPNY2dlPWJcufWHKVjzhHN82mHbivQyFmJZQ99RtVSr/Nx+wkKZB4nImif+CtJ3hFBdIjGQoruvmrbcC+2U6JaNGmSxxlt1/2he5KCjxsjm6S01cCsNR8ivciAuHi1LAoOza0aWELOMPQz09mvgWX92R/Bj5swgpxZoQr3MmytlTncs9S77Fv6WeUh4Em/fIRAeN8ffzK9t87DbjHgfXvdRKcOWTQbhH9wNUf0VeA58NibFktIZbQwP5088G/o4A="
   on:
-    repo: FiloSottile/mkcert
+    repo: drud/mkcert
     tags: true