Revert "Compile everything in Ubuntu builder"

This reverts commit 16c333b1a3.

I tried to build everything in Ubuntu images, but

- this introduced a regression (ignores $BUILD_OPTION)
- made that we don't use -Werror (when we should)

I tried to fix the use of the first, but it would involve more changes
than I prefer. On the second, we cannot enable -Werror, as FlexRIC does
not build warning-free (in Release mode). We thus have to build only the
targets that we require, and therefore we can keep using build_oai,
which is the simplest option (cf. the first point).

docker/Dockerfile.build.ubuntu

@@ -42,15 +42,22 @@ RUN \
    # Mount CPM package cache
    --mount=type=cache,target=/root/.cache/cpm/ \
     /bin/sh oaienv && \
-    mkdir -p cmake_targets/ran_build/build && \
+    cd cmake_targets && \
-    cd cmake_targets/ran_build/build && \
+    mkdir -p log && \
-    cmake ../../../ -GNinja \
+    ./build_oai -c --ninja \
-        -DENABLE_TELNETSRV=ON -DENABLE_ENBSCOPE=ON -DENABLE_UESCOPE=ON -DENABLE_NRSCOPE=ON \
+      --eNB --gNB --RU --UE --nrUE \
-        -DOAI_USRP=ON -DOAI_BLADERF=ON -DOAI_ETHERNET=ON -DOAI_VRTSIM_TAPS_CLIENT=ON \
+      --build-lib "telnetsrv enbscope uescope nrscope" \
-        -DE2_AGENT=ON -DKPM_VERSION=KPM_V3_00 -DE2AP_VERSION=E2AP_V3 \
+      -w USRP -t Ethernet -w BLADERF \
-        -DAVX512=OFF && \
+      --build-e2 --cmake-opt -DKPM_VERSION=$KPM_VERSION --cmake-opt -DE2AP_VERSION=$E2AP_VERSION \
-    # -DCMAKE_C_FLAGS=-Werror -DCMAKE_CXX_FLAGS=-Werror && \
+      --cmake-opt -DOAI_VRTSIM_TAPS_CLIENT=ON \
-    ninja
+      --noavx512 \
+      --build-tool-opt -k10 \
+      --cmake-opt -DCMAKE_C_FLAGS="-Werror" --cmake-opt -DCMAKE_CXX_FLAGS="-Werror" $BUILD_OPTION && \
+    # Mainly to see if the sanitize option was perfectly executed
+    echo "---- ldd on executables ----" && \
+    ldd ran_build/build/*softmodem* ran_build/build/nr-cuup ran_build/build/oairu && \
+    echo "---- ldd on shared libraries ----" && \
+    ldd ran_build/build/*.so
 
 ## Build FlexRIC for SM Models
 RUN \