More powershell fixes
-if ($Env:Platform -eq "x64") { mkdir -Force x64; cd x64 }
-mkdir -Force $Env:Configuration"
+if ($Env:Platform -eq "x64") { mkdir -Force x64; mkdir -Force x64\$Env:Configuration }
+else { mkdir -Force $Env:Configuration }
pwd
-if ($Env:Platform -eq "x64") { cd .. }
-pwd
-msbuild /p:Configuration=$Env:Configuration /p:Platform=$Env:Platform /m .\picoquic.sln
+msbuild "/p:Configuration=$Env:Configuration" "/p:Platform=$Env:Platform" /m .\picoquic.sln
