Fix deprecation warning from Platformio

platformio.ini

@@ -7,7 +7,6 @@ f_cpu = 160000000L
 framework = arduino
 board = esp12e
 build_flags = 	-Wl,-Teagle.flash.4m2m.ld
-src_build_flags = !echo "-DBUILD_TAG="$TRAVIS_TAG
 upload_speed = 460800
 monitor_speed = 115200
 lib_deps =
@@ -31,7 +30,6 @@ board = ${common.board}
 lib_deps = ${common.lib_deps}
 extra_scripts = scripts/GENdeploy.py
 build_flags = ${common.build_flags}
-src_build_flags = ${common.src_build_flags}
 ;https://github.com/platformio/platform-espressif8266/issues/153
 upload_speed = ${common.upload_speed}
 monitor_speed = ${common.monitor_speed}
@@ -46,7 +44,6 @@ board = ${common.board}
 lib_deps = ${common.lib_deps}
 build_flags = ${common.build_flags}
 		-DDEBUG
-src_build_flags = ${common.src_build_flags}
 extra_scripts = scripts/DBGdeploy.py
 upload_speed = ${common.upload_speed}
 monitor_speed = ${common.monitor_speed}