Update devenv script (DataDog#8677)

* Update devenv script

* Cleanup devenv script

Remove things not needed to build an agent binary

* Fix environment on devenv

- When appending to PATH, fetch previous value from the registry, instead of
  using $Env:PATH. This prevents the script from clobbering paths that were
  added by chocolatey install.
- Add rtloader\bin directory to the path, so that agent.exe can find our rtloader.dll.
- Add gopath\bin to the path, so we can run tools installed by go get.

* Add gcloud devenv image builder

devenv/gcloud.pkr.hcl

@@ -0,0 +1,45 @@
+# Packer script to build devenv image on GCP.
+# 
+# Usage:
+#   packer init gcloud.pkr.hcl
+#   packer build gcloud.pkr.hcl
+
+packer {
+  required_plugins {
+    googlecompute = {
+      version = ">= 0.0.1"
+      source = "github.com/hashicorp/googlecompute"
+    }
+  }
+}
+
+source "googlecompute" "datadog-agent-windows-dev" {
+  project_id = 
+  network = 
+  subnetwork = 
+
+  source_image_family = "windows-2019"
+  zone = "europe-west1-b"
+  disk_size = 50
+  machine_type = "e2-standard-4"
+  communicator = "winrm"
+  winrm_username = "packer_user"
+  winrm_insecure = true
+  winrm_use_ssl = true
+  image_name = "agent-windows-dev-{{timestamp}}"
+  image_family = "agent-windows-dev"
+  metadata = {
+    windows-startup-script-cmd = "winrm quickconfig -quiet & net user /add packer_user & net localgroup administrators packer_user /add & winrm set winrm/config/service/auth @{Basic=\"true\"}"
+  }
+}
+
+build {
+  sources = ["sources.googlecompute.datadog-agent-windows-dev"]
+  provisioner "powershell" {
+    scripts = [
+      "scripts/Install-DevEnv.ps1",
+      "scripts/Disable-WinRM.ps1"
+    ]
+  }
+}
+

devenv/scripts/Install-DevEnv.ps1

@@ -27,22 +27,6 @@ cinst -y git
 Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Getting 7zip'
 cinst -y 7zip
 
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Visual Studio build tools'
-cinst -y visualstudio2017buildtools --params "--add Microsoft.VisualStudio.ComponentGroup.NativeDesktop.Win81"
-
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Visual C++ Workload'
-cinst -y visualstudio2017-workload-vctools
-
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installinc VC Tools for Python 2.7'l
-cinst -y vcpython27
-
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Wix'
-cinst -y wixtoolset --version 3.11
-[Environment]::SetEnvironmentVariable(
-    "Path",
-    [Environment]::GetEnvironmentVariable("Path", [EnvironmentVariableTarget]::Machine) + ";${env:ProgramFiles}\WiX Toolset v3.11\bin",
-    [System.EnvironmentVariableTarget]::Machine)
-
 Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing CMake'
 cinst -y cmake
 [Environment]::SetEnvironmentVariable(
@@ -76,30 +60,34 @@ Start-Process "7z" -ArgumentList 'x -oc:\ c:\go.zip' -Wait
 Write-Host -ForegroundColor Green "Removing temporary file $out"
 Remove-Item 'c:\go.zip'
 
-setx GOROOT c:\go
-$Env:GOROOT="c:\go"
-setx PATH "$Env:Path;c:\go\bin;"
-$Env:Path="$Env:Path;c:\go\bin;"
+[Environment]::SetEnvironmentVariable(
+    "Path",
+    [Environment]::GetEnvironmentVariable("Path", [EnvironmentVariableTarget]::Machine) + ";C:\go\bin",
+    [System.EnvironmentVariableTarget]::Machine)
+
+setx /m GOROOT c:\go
 # End Go workaround
 
 Write-Host -ForegroundColor Green "Installed go $ENV:GO_VERSION"
 
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Python 2'
-cinst -y python2
+Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Python 3'
+cinst -y python3
 
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Ruby'
-cinst -y ruby --version 2.4.3.1
+Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing MINGW'
+cinst -y mingw
 
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing MSYS'
-cinst -y msys2 --params "/NoUpdate" # install msys2 without system update
+Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Make'
+cinst -y make
 
-# Reload environment to get ruby in path
-Update-SessionEnvironment
+$GoPath="C:\gopath"
+$AgentPath="$GoPath\src\github.com\datadog\datadog-agent"
+mkdir -Force $AgentPath
 
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Toolchain'
-ridk install 2 3 # use ruby's ridk to update the system and install development toolchain
+[Environment]::SetEnvironmentVariable(
+    "Path",
+    [Environment]::GetEnvironmentVariable("Path", [EnvironmentVariableTarget]::Machine) + ";$GoPath\bin;$AgentPath\rtloader\bin",
+    [System.EnvironmentVariableTarget]::Machine)
 
-Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen '- Installing Bundler'
-gem install bundler
+setx /m GOPATH "$GoPath"
 
 Write-Host -ForegroundColor Yellow -BackgroundColor DarkGreen ' * DONE *'