build(app): print RMM Core offset during build

Since apps are now packaged into RMM binary, for symbol debug
of RMM, the offset of RMM core from start of bin needs to
be taken into consideration. Having this print from build
log is useful for developers. Note that this info
is also present in <build>/Debug/bundle_app_out.txt
in case of a Debug build.

A sample print is given below:
"INFO: The offset of the RMM bin is 122880 (0x1e000) bytes"

Signed-off-by: Jacob Man Chun Yiu <jacobmanchun.yiu@arm.com>
Change-Id: Iaadb825f206c50accf408175560c54f7ceab765f
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d6bcd5a..a0bacd3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -173,7 +173,7 @@
 
     set(BUNDLE_COMMAND_OUTPUT "${ARTEFACT_DIR}/bundle_app_out.txt")
     add_custom_command(
-        COMMAND "${BUNDLE_APP_RMM}" --out-bin ${ARTEFACT_DIR}/${RMM_IMG} --rmm-bin ${ARTEFACT_DIR}/rmm_core.img ${EL0_APP_BIN_LIST} 2> ${BUNDLE_COMMAND_OUTPUT}
+        COMMAND "${BUNDLE_APP_RMM}" --out-bin ${ARTEFACT_DIR}/${RMM_IMG} --rmm-bin ${ARTEFACT_DIR}/rmm_core.img --log-file-name ${BUNDLE_COMMAND_OUTPUT} ${EL0_APP_BIN_LIST}
         OUTPUT ${RMM_IMG}
         DEPENDS rmm_core.img rmm-random-app-bin rmm-attestation-app-bin)
 endif()