Windows: add install directory to the Path environment variable

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/os/windows/install.wxs b/os/windows/install.wxs
index fd38041..fc853d3 100755
--- a/os/windows/install.wxs
+++ b/os/windows/install.wxs
@@ -25,6 +25,7 @@
 					<Directory Id="fio" Name="fio">
 						<Component>
 							<File Source="..\..\fio.exe"/>
+							<Environment Action="set" Part="last" Id="PATH" Name="PATH" Value="[INSTALLDIR]fio\" System="yes"/>
 						</Component>
 						<Component>
 							<File Id="README" Name="README.txt" Source="..\..\README"/>