Try new syntaw in dockerfile

Dockerfile

@@ -63,7 +63,7 @@ RUN --mount=type=secret,id=proxy_http_cnes --mount=type=secret,id=proxy_https_cn
     if [ -f "/run/secrets/proxy_https_cnes" ]; then export https_proxy=$(cat /run/secrets/proxy_https_cnes); fi && \
     mkdir -p /root/otb-build/build && \
     cd /root/otb-build && \
-    if [ ! -z ${https_proxy+x} ]; then wget -e use_proxy=yes -e https_proxy=$https_proxy -e http_proxy=$http_proxy -q https://www.orfeo-toolbox.org/packages/archives/OTB/OTB-7.0.0.zip -O /tmp/OTB.zip; else wget -q https://www.orfeo-toolbox.org/packages/archives/OTB/OTB-7.0.0.zip -O /tmp/OTB.zip; fi && \
+    if [ -f "/run/secrets/proxy_https_cnes" ]; then wget -e use_proxy=yes -e https_proxy=${https_proxy} -e http_proxy=${http_proxy} -q https://www.orfeo-toolbox.org/packages/archives/OTB/OTB-7.0.0.zip -O /tmp/OTB.zip; else wget -q https://www.orfeo-toolbox.org/packages/archives/OTB/OTB-7.0.0.zip -O /tmp/OTB.zip; fi && \
     unzip /tmp/OTB.zip && \
     cd /root/otb-build/build && \
     cmake \