Merge remote-tracking branch 'origin/fast-u22-build' into integration_2025_w25 (!3083)

Speed up ubuntu22 image build

Speed up softmodems build by means of:
- Avoiding the copying the repo (using bind instead)
- Creating cache directories for:
  - ccache cache
  - CPM cache
  - Same technique applied to FlexRIC build
- Make ubuntu ran-base image docker build cache friendly

docker/Dockerfile.base.ubuntu22

@@ -40,6 +40,7 @@ RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get install --yes \
        #gcc needed for build_oai
        build-essential \
+       ccache \
        psmisc \
        git \
        #use gcc-12 to avoid problems of default gcc-11 in FlexRIC
@@ -52,15 +53,15 @@ RUN apt-get update && \
        flex \
        m4 \
        # python3-pip for conf template generation
-       python3-pip && \
+       python3-pip \
+       wget && \
     update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-12 100 --slave /usr/bin/g++ g++ /usr/bin/g++-12 && \
     pip3 install --ignore-installed pyyaml
 
 # 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/${TINI_VERSION}/tini-${TARGETARCH} /tini
-RUN chmod +x /tini
+RUN wget https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini-${TARGETARCH} -O /tini && chmod +x /tini
 
 # In some network environments, GIT proxy is required
 RUN /bin/bash -c "if [[ -v NEEDED_GIT_PROXY ]]; then git config --global http.proxy $NEEDED_GIT_PROXY; fi"

docker/Dockerfile.build.ubuntu22

@@ -36,7 +36,12 @@ WORKDIR /oai-ran
 COPY . .
 
 # build all targets so final targets can be created afterwards
-RUN /bin/sh oaienv && \
+RUN \
+   # Mount CCache cache direrctory
+   --mount=type=cache,target=/root/.cache/ccache/ \
+   # Mount CPM package cache
+   --mount=type=cache,target=/root/.cache/cpm/ \
+    /bin/sh oaienv && \
     cd cmake_targets && \
     mkdir -p log && \
     ./build_oai -c --ninja \
@@ -54,7 +59,10 @@ RUN /bin/sh oaienv && \
     ldd ran_build/build/*.so
 
 ## Build FlexRIC for SM Models
-RUN mkdir -p openair2/E2AP/flexric/build && \
+RUN \
+    # Mount CCache cache direrctory
+    --mount=type=cache,target=/root/.cache/ccache/ \
+    mkdir -p openair2/E2AP/flexric/build && \
     cd openair2/E2AP/flexric/build && \
     cmake -GNinja -DCMAKE_BUILD_TYPE=Release \
           -DKPM_VERSION=$KPM_VERSION \