Fix Makefile on Windows and use in AppVeyor build (#3748)

Makefile

@@ -2,7 +2,7 @@ PREFIX := /usr/local
 VERSION := $(shell git describe --exact-match --tags 2>/dev/null)
 BRANCH := $(shell git rev-parse --abbrev-ref HEAD)
 COMMIT := $(shell git rev-parse --short HEAD)
-GOFILES ?= $(shell find . -name '*.go')
+GOFILES ?= $(shell git ls-files '*.go')
 GOFMT ?= $(shell gofmt -l $(GOFILES))
 
 ifdef GOBIN

appveyor.yml

@@ -13,20 +13,21 @@ platform: x64
 install:
   - IF NOT EXIST "C:\Cache" mkdir C:\Cache
   - IF NOT EXIST "C:\Cache\go1.9.2.msi" curl -o "C:\Cache\go1.9.2.msi" https://storage.googleapis.com/golang/go1.9.2.windows-amd64.msi
+  - IF NOT EXIST "C:\Cache\gnuwin32-bin.zip" curl -o "C:\Cache\gnuwin32-bin.zip" https://dl.influxdata.com/telegraf/ci/make-3.81-bin.zip
+  - IF NOT EXIST "C:\Cache\gnuwin32-dep.zip" curl -o "C:\Cache\gnuwin32-dep.zip" https://dl.influxdata.com/telegraf/ci/make-3.81-dep.zip
   - IF EXIST "C:\Go" rmdir /S /Q C:\Go
   - msiexec.exe /i "C:\Cache\go1.9.2.msi" /quiet
+  - 7z x "C:\Cache\gnuwin32-bin.zip" -oC:\GnuWin32 -y
+  - 7z x "C:\Cache\gnuwin32-dep.zip" -oC:\GnuWin32 -y
   - go version
   - go env
 
 build_script:
-  - cmd: go get github.com/sparrc/gdm
-  - cmd: C:\gopath\bin\gdm restore
-  - cmd: go build -i -o telegraf.exe ./cmd/telegraf/telegraf.go
+  - cmd: C:\GnuWin32\bin\make deps
+  - cmd: C:\GnuWin32\bin\make telegraf
 
 test_script:
-  - cmd: go test ./plugins/inputs/ping/...
-  - cmd: go test ./plugins/inputs/win_perf_counters/...
-  - cmd: go test ./plugins/inputs/win_services/...
+  - cmd: C:\GnuWin32\bin\make test-windows
 
 artifacts:
   - path: telegraf.exe