bionic-amd64-tf-a-build: include Node.js v14 (LTS)

We are introducing additional Node.js tools that depend on Node.js, as
well as associated CI checks which use them (`commitlint`).

Change-Id: Ia4bbfe5aa57a0cc7acafa821d44270a4886a0853
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/bionic-amd64-tf-a-build/Dockerfile b/bionic-amd64-tf-a-build/Dockerfile
index 5c25223..5c29f83 100644
--- a/bionic-amd64-tf-a-build/Dockerfile
+++ b/bionic-amd64-tf-a-build/Dockerfile
@@ -7,6 +7,7 @@
 ENV TOOLS_DIR=/home/buildslave/tools
 ENV PATH=${TOOLS_DIR}/bin:${PATH}
 ENV PLANTUML_JAR_PATH=/usr/share/plantuml/plantuml.jar
+ENV NVM_DIR=/usr/local/nvm
 ENV PKG_DEPS="\
     bc \
     bison \
@@ -87,6 +88,13 @@
     bash -ex /tmp/tf-environment.install ;\
     # Fix permissions
     chown -R buildslave:buildslave ${TOOLS_DIR} /usr/share/plantuml /nfs/downloads/linaro /arm ;\
+    # Install NVM
+    mkdir -p ${NVM_DIR} ;\
+    curl -s https://raw.githubusercontent.com/nvm-sh/nvm/v0.38.0/install.sh | bash ;\
+    echo ". ${NVM_DIR}/nvm.sh" >> /home/buildslave/.bashrc ;\
+    chown -R buildslave:buildslave /home/buildslave/.bashrc ;\
+    . ${NVM_DIR}/nvm.sh ;\
+    nvm install 14 ;\
     # Cleanup
     apt clean ;\
     rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*