TF: add plantuml wrapper script

TF-A documentation build triggers the following python exception:

    Exception occurred:
      File "/usr/local/lib/python3.6/dist-packages/sphinxcontrib/plantuml.py", line 352, in _prepare_html_render
        self.builder.warn(str(err))
    AttributeError: 'StandaloneHTMLBuilder' object has no attribute 'warn'
    The full traceback has been saved in /tmp/sphinx-err-oyao8gvj.log, if you want to report the issue to the developers.
    Please also report this if it was a user error, so that a better error message can be provided next time.
    A bug report can be filed in the tracker at <https://github.com/sphinx-doc/sphinx/issues>. Thanks!
    Makefile:25: recipe for target 'html' failed
    make[2]: *** [html] Error 2
    Makefile:1295: recipe for target 'doc' failed
    make[1]: *** [doc] Error 2

It's caused by sphinx trying to run plantuml command which doesn't exist
since we install the jar manually. Add a wrapper shell script to fix the
issue.

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
Change-Id: Ie48273ee50581ca7c32f13629f6e95b18882b912
diff --git a/bionic-amd64-tf-m-build/tf-dependencies.install b/bionic-amd64-tf-m-build/tf-dependencies.install
index 95e1d13..4470248 100755
--- a/bionic-amd64-tf-m-build/tf-dependencies.install
+++ b/bionic-amd64-tf-m-build/tf-dependencies.install
@@ -10,6 +10,11 @@
 # Install PlantUML
 curl --create-dirs -fsSLo ${PLANTUML_JAR_PATH} \
   https://repo1.maven.org/maven2/net/sourceforge/plantuml/plantuml/1.2019.6/plantuml-1.2019.6.jar
+cat << EOF > /usr/bin/plantuml
+#!/bin/sh
+/usr/bin/java -jar ${PLANTUML_JAR_PATH} \${@}
+EOF
+chmod 0755 /usr/bin/plantuml
 
 # Install CMake
 curl --connect-timeout 5 --retry 5 --retry-delay 1 --create-dirs -fsSLo /tmp/cmake-Linux-x86_64.tar.gz \