From http://code.google.com/p/dbup/source/browse/build.ps1

build.ps1

# effectively this is VB's Option Strict On but for PowerShell
$ErrorActionPreference = 'Stop'
Set-StrictMode -Version Latest

$buildFile = "build\Build.proj"

# simulate the variable representing the folder this script is in (a PS Module would get this by default)
$PSScriptRoot = ($MyInvocation.MyCommand.Path | Split-Path | Resolve-Path).ProviderPath 

# never pass relative paths outside your script
$absoluteBuildFile = $PSScriptRoot | Join-Path -ChildPath $buildFile

# ask the registry for the path to the .NET 4.0 framework. 
# there is a better API but to ask for the .NET 4 path you need to be running CLR 4 and PowerShell is only CLR 2
$fxPath = (Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full").InstallPath

# build as per normal but passing the full project path
$msbuildPath = Join-Path -Path $fxPath -ChildPath "MSBuild.exe"
& $msbuildpath $absoluteBuildfile /t:Build /v:m

# PowerShell often ignores the exit code of external commands, let's check explicitly
# (the ISE and PS Remoting sessions however will detect STDERR output and convert that to PS errors)
if (-not $?) { throw "MSBuild failed with exit code $LastExitCode" }