Simplify compilations build helper

Instead of using ninja/make directly, there is a cmake command option to
trigger the build using whatever build tool has been configured. Use it;
if there is a mismatch, there will also be a clearer cmake error.

Remove build_oai's --build-coverity: we don't use it, and it can
trivially be added if required (probably, most users would run it by
hand anyway).

Add an error if the compilations function is not called with the right
noumber of arguments.

cmake_targets/tools/build_helper

@@ -216,36 +216,26 @@ check_errors() {
 }
 
 compilations() {
+  [[ $# -gt 2 ]] || echo_fatal "compilations needs more than three arguments"
   local dir=$1
   shift 1
   local logfile=$1
   shift 1
   local targets=$@
+  local verbose=$([ "$VERBOSE_COMPILE" == "1" ] && echo "-v" || echo "")
+  echo cd $OPENAIR_DIR/cmake_targets/$dir/build
   cd $OPENAIR_DIR/cmake_targets/$dir/build
-  cecho "Running \"$MAKE_CMD $targets\"" $green
-  echo_info "Log file for compilation is being written to: $dlog/$logfile"
+  echo_info "Running \"cmake --build . $verbose --target $targets -- -j$(nproc)\"" $green
+  echo "Log file for compilation is being written to: $dlog/$logfile"
   set +e
   {
-    if [ "$BUILD_COVERITY_SCAN" == "1" ]; then
-        COV_SCAN_PREFIX="cov-build --dir cov-int"
-    else
-        COV_SCAN_PREFIX=""
-    fi
-    if [ "$MAKE_CMD" != "" ]; then
-       $MAKE_CMD $targets
-    else 
-    if [ "$VERBOSE_COMPILE" == "1" ]; then
-       $COV_SCAN_PREFIX make -j`nproc` $targets VERBOSE=$VERBOSE_COMPILE
-    else
-       $COV_SCAN_PREFIX make -j`nproc` $targets
-    fi
-    fi
+    cmake --build . $verbose --target $targets -- -j$(nproc)
     ret=$?
   } > $dlog/$logfile 2>&1
   if [ "$VERBOSE_CI" == "1" ]; then
-     echo_info "====== Start of log for $logfile ======"
+     echo "====== Start of log for $logfile ======"
      cat $dlog/$logfile
-     echo_info "====== End of log for $logfile ======"
+     echo "====== End of log for $logfile ======"
   fi
   check_warnings "$dlog/$logfile"
   if [[ $ret -eq 0 ]]; then