tfs: fix concurrent windows builds

build/tfs/win32/lib.ps1

@@ -1,8 +1,11 @@
 # stop when there's an error
 $ErrorActionPreference = 'Stop'
 
-# set agent specific npm cache
 if (Test-Path env:AGENT_WORKFOLDER) {
+	# will be used by node-gyp
+	$env:HOME = "${env:AGENT_WORKFOLDER}\home"
+
+	# will be used by npm
 	$env:npm_config_cache = "${env:AGENT_WORKFOLDER}\npm-cache"
 }
 

scripts/env.ps1

@@ -1,5 +1,5 @@
 $env:npm_config_disturl="https://atom.io/download/electron"
 $env:npm_config_target=(node -p "require('./package.json').electronVersion")
 $env:npm_config_runtime="electron"
-$env:npm_config_cache="$HOME/.npm-electron"
+$env:npm_config_cache="${env:USERPROFILE}/.npm-electron"
 New-Item -Path "$env:npm_config_cache" -Type directory -Force | out-null