This PowerShell script will change your Sitecore instance search provider from Lucene to Solr or vice versa. It can be called from a build process to do so.

ChangeSearchProvider.ps1

Function Set-SCSearchProvider
{
	param([string]$choice, [string]$rootPath)

    $validInput = $true;
    #test that path is valid
    If (!(Test-Path -Path $rootPath))
    {
        Write-Host "The supplied path was invalid or inaccessible." -ForegroundColor Red;
        $validInput = $false;
    }
    #test that choice is valid
    ElseIf (($choice -ne "L") -and ($choice -ne "S"))
    {
        Write-Host "You must choose L or S." -ForegroundColor Red;
        $validInput = $false;
    }
    

    If ($validInput)
    {
        If (($choice -eq "L"))
        {
            Write-Host "Set to Lucene." -ForegroundColor Yellow;
            $selectedProvider = "Lucene";
            $deselectedProvider = "Solr";
        }
        ElseIf (($choice -eq "S"))
        {
            Write-Host "Set to Solr." -ForegroundColor Yellow;
            $selectedProvider = "Solr";
            $deselectedProvider = "Lucene";
        }

        #enumerate all config files to be enabled
        $filter = "*" + $selectedProvider + "*.config*";
        $selectedProviderFiles = Get-ChildItem -Recurse -File -Path $rootPath -Filter $filter;
        foreach ($file in $selectedProviderFiles)
        {
            Write-Host $file.Name;
			if (($file.Extension -ne ".config"))
            {
                $newDestination = [io.path]::GetDirectoryName($file.FullName) + "\" + [io.path]::GetFileNameWithoutExtension($file.FullName);
                $newFile = Move-Item -Path $file.FullName -Destination $newDestination -Force -PassThru;
                Write-Host "-> " $newFile.Name -ForegroundColor Green;
            }
        }

        #enumerate all config files to be disabled
        $filter = "*" + $deselectedProvider + "*.config*";
        $deselectedProviderFiles = Get-ChildItem -Recurse -File -Path $rootPath -Filter $filter;
        foreach ($file in $deselectedProviderFiles)
        {
            Write-Host $file.Name;
            if ($file.Extension -eq ".config")
            {
                $newDestination = [io.path]::GetDirectoryName($file.FullName) + "\" + $file.Name + ".disabled";
                $newFile = Move-Item -Path $file.FullName -Destination $newDestination -Force -PassThru;
                Write-Host "-> " $newFile.Name -ForegroundColor Green;
            }
        }
    }
}

Set-SCSearchProvider $args[0] $args[1]