builder: set buildkit's exported product variable via PRODUCT

This introduces a PRODUCT environment variable that is used to set a constant
at dockerversion.ProductName.

That is then used to set BuildKit's ExportedProduct variable in order to show
useful error messages to users when a certain version of the product doesn't
support a BuildKit feature.

Signed-off-by: Tibor Vass <tibor@docker.com>
Upstream-commit: 195919d9d645aa4ab5680a2331c57ff33eb9e5d9
Component: engine

components/engine/hack/make.ps1

@@ -365,7 +365,7 @@ Try {
     # Run autogen if building binaries or running unit tests.
     if ($Client -or $Daemon -or $TestUnit) {
         Write-Host "INFO: Invoking autogen..."
-        Try { .\hack\make\.go-autogen.ps1 -CommitString $gitCommit -DockerVersion $dockerVersion -Platform "$env:PLATFORM" }
+        Try { .\hack\make\.go-autogen.ps1 -CommitString $gitCommit -DockerVersion $dockerVersion -Platform "$env:PLATFORM" -Product "$env:PRODUCT" }
         Catch [Exception] { Throw $_ }
     }
 

components/engine/hack/make/.go-autogen

@@ -21,6 +21,7 @@ const (
 	IAmStatic          string = "${IAMSTATIC:-true}"
 	ContainerdCommitID string = "${CONTAINERD_COMMIT}"
 	PlatformName       string = "${PLATFORM}"
+	ProductName        string = "${PRODUCT}"
 )
 
 // AUTOGENERATED FILE; see /go/src/github.com/docker/docker/hack/make/.go-autogen

components/engine/hack/make/.go-autogen.ps1

@@ -15,7 +15,8 @@
 param(
     [Parameter(Mandatory=$true)][string]$CommitString,
     [Parameter(Mandatory=$true)][string]$DockerVersion,
-    [Parameter(Mandatory=$false)][string]$Platform
+    [Parameter(Mandatory=$false)][string]$Platform,
+    [Parameter(Mandatory=$false)][string]$Product
 )
 
 $ErrorActionPreference = "Stop"
@@ -45,6 +46,7 @@ const (
     Version            string = "'+$DockerVersion+'"
     BuildTime          string = "'+$buildDateTime+'"
     PlatformName       string = "'+$Platform+'"
+    ProductName        string = "'+$Product+'"
 )
 
 // AUTOGENERATED FILE; see hack\make\.go-autogen.ps1