Restructured NBI Dockerfile to prevent rebilding libyang too frequently

src/nbi/Dockerfile

@@ -16,9 +16,24 @@ FROM python:3.9-slim
 
 # Install dependencies
 RUN apt-get --yes --quiet --quiet update && \
-    apt-get --yes --quiet --quiet install wget g++ git && \
+    apt-get --yes --quiet --quiet install wget g++ git build-essential cmake libpcre2-dev python3-dev python3-cffi && \
     rm -rf /var/lib/apt/lists/*
 
+# Download, build and install libyang. Note that APT package is outdated
+# - Ref: https://github.com/CESNET/libyang
+# - Ref: https://github.com/CESNET/libyang-python/
+RUN mkdir -p /var/libyang
+RUN git clone https://github.com/CESNET/libyang.git /var/libyang
+WORKDIR /var/libyang
+RUN git fetch
+RUN git checkout v2.1.148
+RUN mkdir -p /var/libyang/build
+WORKDIR /var/libyang/build
+RUN cmake -D CMAKE_BUILD_TYPE:String="Release" ..
+RUN make
+RUN make install
+RUN ldconfig
+
 # Set Python to show logs as they occur
 ENV PYTHONUNBUFFERED=0
 
@@ -53,24 +68,6 @@ RUN python3 -m grpc_tools.protoc -I=. --python_out=. --grpc_python_out=. *.proto
 RUN rm *.proto
 RUN find . -type f -exec sed -i -E 's/(import\ .*)_pb2/from . \1_pb2/g' {} \;
 
-# Download, build and install libyang. Note that APT package is outdated
-# - Ref: https://github.com/CESNET/libyang
-# - Ref: https://github.com/CESNET/libyang-python/
-RUN apt-get --yes --quiet --quiet update && \
-    apt-get --yes --quiet --quiet install build-essential cmake libpcre2-dev python3-dev python3-cffi && \
-    rm -rf /var/lib/apt/lists/*
-RUN mkdir -p /var/libyang
-RUN git clone https://github.com/CESNET/libyang.git /var/libyang
-WORKDIR /var/libyang
-RUN git fetch
-RUN git checkout v2.1.148
-RUN mkdir -p /var/libyang/build
-WORKDIR /var/libyang/build
-RUN cmake -D CMAKE_BUILD_TYPE:String="Release" ..
-RUN make
-RUN make install
-RUN ldconfig
-
 # Create component sub-folders, get specific Python packages
 RUN mkdir -p /var/teraflow/nbi
 WORKDIR /var/teraflow/nbi