compilation warning "jobserver unavailable" removal

This commit removes the warning:
make[4]: warning: jobserver unavailable: using -j1.  Add '+' to parent make rule.

Basically, inside a Makefile we should use $(MAKE) instead of make.

cmake_targets/CMakeLists.txt

@@ -1880,9 +1880,9 @@ endif (${T_TRACER})
 #This rule and the following deal with it.
 add_custom_command (
   OUTPUT ${OPENAIR_DIR}/common/utils/T/T_IDs.h
-  COMMAND make clean
-  COMMAND make
-  COMMAND make check_vcd
+  COMMAND $(MAKE) clean
+  COMMAND $(MAKE)
+  COMMAND $(MAKE) check_vcd
   WORKING_DIRECTORY ${OPENAIR_DIR}/common/utils/T
   DEPENDS ${OPENAIR_DIR}/common/utils/T/T_messages.txt
           ${OPENAIR_DIR}/common/utils/LOG/vcd_signal_dumper.c
@@ -2235,7 +2235,7 @@ function(make_driver name dir)
   endforeach()
   CONFIGURE_FILE(${OPENAIR_CMAKE}/tools/Kbuild.cmake ${OPENAIR_BIN_DIR}/${name}/Kbuild)
   add_custom_command(OUTPUT ${name}.ko
-    COMMAND make -C ${module_build_path} M=${OPENAIR_BIN_DIR}/${name}
+    COMMAND $(MAKE) -C ${module_build_path} M=${OPENAIR_BIN_DIR}/${name}
     WORKING_DIRECTORY ${OPENAIR_BIN_DIR}/${name}
     COMMENT "building ${module}.ko"
     VERBATIM