Fix for reusing of externals build

Second try to caching the externals build. The improvement compared to !32965 (merged) (reverted in !33206 (merged)) is to include the upstream (Athena) project version in the externals stamp file. That way we are rebuilding (and more importantly reinstalling) the externals in case the upstream version changes. Otherwise it would not be found under the release version (ATLINFR-3018).

Also implement the same caching now for AnalysisBase.

cc @akraszna

Projects/AnalysisBase/build_externals.sh

@@ -82,12 +82,23 @@ if [ "$FORCE" = "1" ]; then
     rm -fr ${BUILDDIR}/build/AnalysisBaseExternals
 fi
 
-# Create some directories:
-mkdir -p ${BUILDDIR}/{src,install}
-
 # Get the version of AnalysisBase for the build.
 version=`cat ${thisdir}/version.txt`
 
+# Check if previous externals build can be reused:
+externals_stamp=${BUILDDIR}/build/AnalysisBaseExternals/externals-${version}.stamp
+if [ -f ${externals_stamp} ]; then
+    if diff -q ${externals_stamp} ${thisdir}/externals.txt; then
+        echo "Correct version of externals already available in ${BUILDDIR}"
+        exit 0
+    else
+        rm ${externals_stamp}
+    fi
+fi
+
+# Create some directories:
+mkdir -p ${BUILDDIR}/{src,install}
+
 # The directory holding the helper scripts:
 scriptsdir=${thisdir}/../../Build/AtlasBuildScripts
 scriptsdir=$(cd ${scriptsdir}; pwd)
@@ -117,3 +128,6 @@ ${scriptsdir}/build_atlasexternals.sh \
     -i ${BUILDDIR}/install \
     -p AnalysisBaseExternals ${RPMOPTIONS} -t ${BUILDTYPE} \
     -v ${version} ${EXTRACMAKE[@]/#/-x }
+
+# Due to 'set -e' only gets here on success:
+cp ${thisdir}/externals.txt ${externals_stamp}