build: update LDFLAGS for windows

Makefile

@@ -1,6 +1,6 @@
-LDFLAGS = $(shell go run buildscripts/gen-ldflags.go)
+LDFLAGS := $(shell go run buildscripts/gen-ldflags.go)
 DOCKER_LDFLAGS = '-extldflags "-static"'
-TAG = latest
+TAG := latest
 
 all: install
 
@@ -55,7 +55,7 @@ test: build
 	@GO15VENDOREXPERIMENT=1 go test $(GOFLAGS) github.com/minio/minio/pkg...
 
 gomake-all: build
-	@GO15VENDOREXPERIMENT=1 go build --ldflags $(LDFLAGS) -o $(GOPATH)/bin/minio
+	GO15VENDOREXPERIMENT=1 go build --ldflags $(LDFLAGS) -o $(GOPATH)/bin/minio
 
 pkg-add:
 	@GO15VENDOREXPERIMENT=1 govendor add $(PKG)

appveyor.yml

@@ -28,7 +28,7 @@ build_script:
   - go test -race github.com/minio/minio/pkg...
   - go run buildscripts/gen-ldflags.go > temp.txt
   - set /p LDFLAGS=<temp.txt
-  - go build -ldflags=%LDFLAGS% -o %GOPATH%\bin\minio.exe
+  - go build --ldflags %LDFLAGS% -o %GOPATH%\bin\minio.exe
 
 # to disable automatic tests
 test: off