Adds immediate migration state in search of rpm build tools for ubuntu 26.04

Dockerfile-ubuntu26-qt6.dockerfile

@@ -138,10 +138,25 @@ RUN apt-get update \
     && rm -rf /var/lib/apt/lists/*
 
 # Add RPM/rpmbuild tools for make_rpm.py
+# Note: Ubuntu uses different package names than openSUSE/Fedora
+# - rpm: provides rpmbuild command
+# - rpm-common: provides RPM macros and build infrastructure
+# - rpmdevtools is NOT available on Ubuntu, we create directory structure manually
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends rpm rpm-build rpmdevtools \
+    && apt-get install -y --no-install-recommends rpm rpm-common librpmbuild9 \
     && rm -rf /var/lib/apt/lists/*
 
+# Setup rpmbuild directory structure (normally done by rpmdev-setuptree on Fedora/openSUSE)
+RUN mkdir -p /shd/CTC/TOOLS/rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS} \
+    && chown -R ctc:ctc /shd/CTC/TOOLS/rpmbuild
+
+# Copy RTI Connext DDS (proprietary, must be provided externally)
+# RTI is copied from ./external/rti_connext_dds-7.7.0 in the repository
+COPY external/rti_connext_dds-7.7.0 /opt/RTI
+
+# Set DDS_PATH for RTI discovery
+ENV DDS_PATH=/opt/RTI
+
 # Cleanup
 RUN apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*