Added build script for building packages on Windows

build.ps1

@@ -0,0 +1,41 @@
+ param (
+    [string]$SHA = ""
+ )
+
+if ($SHA -eq ""){
+    $SHA = (git rev-parse HEAD) | Out-String
+    $SHA = $SHA.Replace([System.Environment]::NewLine,"")
+}
+
+
+$PKG = "github.com/StackExchange/dnscontrol"
+$DATE = [int][double]::Parse((Get-Date -UFormat %s))
+$FLAGS="-s -w -X main.SHA=$SHA -X main.BuildTime=$DATE"
+Write-Host $FLAGS
+
+$OrigGOOS = $env:GOOS
+
+Write-Host 'Building Linux'
+$env:GOOS = "linux"
+go build -o dnscontrol-Linux -ldflags "$FLAGS" $PKG
+
+Write-Host 'Building Windows'
+$env:GOOS = "windows"
+go build -o dnscontrol.exe -ldflags "$FLAGS" $PKG
+
+Write-Host 'Building Darwin'
+$env:GOOS = "darwin"
+go build -o dnscontrol-Darwin -ldflags "$FLAGS" $PKG
+
+$env:GOOS = $OrigGOOS
+
+#No compression if building on windows
+<#
+if [ "$COMPRESS" = "1" ]
+then
+    echo 'Compressing executables'
+    upx dnscontrol.exe
+    upx dnscontrol-Linux
+    upx dnscontrol-Darwin
+fi
+#>