IIS for PHP: You are missing: jpegtran, optipng, gifsicle

We have WordPress installed with PHP for IIS.
The plugin says the following error messages:

EWWW Image Optimizer uses jpegtran, optipng, pngout, pngquant, gifsicle, and cwebp. You are missing: jpegtran, optipng, gifsicle. Please install via the Settings Page or the Installation Instructions.

However, the files are clearly there, and permissions are Full Control.

Debug Log

[16-May-2016 20:39:49 UTC] PHP Notice: The called constructor method for WP_Widget in html_javascript_adder_widget is deprecated since version 4.3.0! Use
<pre>__construct()</pre>
instead. in C:\inetpub\Virtual Directories\Wordpress\wp-includes\functions.php on line 3718
[16-May-2016 20:39:50 UTC] PHP Notice: The called constructor method for WP_Widget in html_javascript_adder_widget is deprecated since version 4.3.0! Use
<pre>__construct()</pre>
instead. in C:\inetpub\Virtual Directories\Wordpress\wp-includes\functions.php on line 3718
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [“C:\inetpub\Virtual Directories\Wordpress/wp-content/ewww/jpegtran.exe” -v C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer/images/sample.jpg 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 954
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [jpegtran.exe -v C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer/images/sample.jpg 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 954
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [“C:\inetpub\Virtual Directories\Wordpress/wp-content/ewww/optipng.exe” -v 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 978
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [optipng.exe -v 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 978
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [“C:\inetpub\Virtual Directories\Wordpress/wp-content/ewww/gifsicle.exe” –version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1000
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [gifsicle.exe –version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1000
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [ -v C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer/images/sample.jpg 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 954
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [ -copy none -optimize -outfile “C:\inetpub\Virtual Directories\Wordpress/wp-content/uploads/testopti.jpg” “C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer/images/testorig.jpg”] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 966
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [ -v 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 978
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [ -out “C:\inetpub\Virtual Directories\Wordpress/wp-content/uploads/testopti.png” -o1 -quiet -strip all “C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer/images/testorig.png”] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 988
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [ –version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1000
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [ -O3 -o “C:\inetpub\Virtual Directories\Wordpress/wp-content/uploads/testopti.gif” “C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer/images/testorig.gif”] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1010
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [convert -version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1066
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [/usr/bin/convert -version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1066
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [/usr/local/bin/convert -version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1066
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [/usr/gnu/bin/convert -version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1066
[16-May-2016 20:39:51 UTC] PHP Warning: exec(): Unable to fork [/usr/syno/bin/convert -version 2>&1] in C:\inetpub\Virtual Directories\Wordpress\wp-content\plugins\ewww-image-optimizer\ewww-image-optimizer.php on line 1066

https://ww.wp.xz.cn/plugins/ewww-image-optimizer/