build_oai/build_helper: use $CMAKE

Some distributions, e.g., CentOS8 or RHEL8, ship with an old cmake
(v2.8). To provide a newer, they have a separate cmake3 package, where a
recent cmake version is in program cmake3. To be agnostic, build_helper
detects the distribution and choses the cmake program to use.

This commit uses the correct cmake, which is provided in the environment
variable $CMAKE.

cmake_targets/build_oai

@@ -523,7 +523,7 @@ function main() {
     echo_info "Doxygen generation log is located here: $doxygen_log"
     echo_info "Generating Doxygen files....please wait"
     (
-      cmake --build . --target doc
+      $CMAKE --build . --target doc
     ) >& $doxygen_log
   fi
 

cmake_targets/tools/build_helper

@@ -226,11 +226,11 @@ compilations() {
   local verbose=$([ "$VERBOSE_COMPILE" == "1" ] && echo "-v" || echo "")
   echo cd $OPENAIR_DIR/cmake_targets/$dir/build
   cd $OPENAIR_DIR/cmake_targets/$dir/build
-  echo_info "Running \"cmake --build . $verbose --target $targets -- -j$(nproc)\"" $green
+  echo_info "Running \"$CMAKE --build . $verbose --target $targets -- -j$(nproc)\"" $green
   echo "Log file for compilation is being written to: $dlog/$logfile"
   set +e
   {
-    cmake --build . $verbose --target $targets -- -j$(nproc)
+    $CMAKE --build . $verbose --target $targets -- -j$(nproc)
     ret=$?
   } > $dlog/$logfile 2>&1
   if [ "$VERBOSE_CI" == "1" ]; then