fix(docker): making tini download platform specific to support ARM64 native builds

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

docker/Dockerfile.base.rhel9

@@ -29,6 +29,7 @@
 FROM registry.access.redhat.com/ubi9/ubi:latest AS ran-base
 LABEL MAINTAINER OpenAirInterface <contact@openairinterface.org>
 ARG NEEDED_GIT_PROXY
+ARG TARGETARCH
 ENV TZ=Europe/Paris
 ENV BUILD_UHD_FROM_SOURCE=True
 ENV UHD_VERSION=4.4.0.0
@@ -68,7 +69,7 @@ RUN rm -f /etc/rhsm-host && \
 # Add "Tini - A tiny but valid init for containers", https://github.com/krallin/tini
 # it will be copied into target containers, to print exit numbers and handle signals properly
 ENV TINI_VERSION=v0.19.0
-ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini /tini
+ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini-${TARGETARCH} /tini
 RUN chmod +x /tini
 
 # In some network environments, GIT proxy is required