Update 'board_f_cpu' to 'board_build.f_cpu'

platformio.ini

 #
 
 [platformio]
-src_dir = Marlin
-build_dir = .pioenvs
-lib_dir = .piolib
+src_dir     = Marlin
+build_dir   = .pioenvs
+lib_dir     = .piolib
 libdeps_dir = .piolibdeps
 env_default = megaatmega2560
 
 # ATmega2560
 #
 [env:megaatmega2560]
-platform      = atmelavr
-framework     = arduino
-board         = megaatmega2560
-build_flags   = ${common.build_flags}
-board_f_cpu   = 16000000L
-lib_deps      = ${common.lib_deps}
-src_filter    = ${common.default_src_filter}
-monitor_speed = 250000
+platform          = atmelavr
+framework         = arduino
+board             = megaatmega2560
+build_flags       = ${common.build_flags}
+board_build.f_cpu = 16000000L
+lib_deps          = ${common.lib_deps}
+src_filter        = ${common.default_src_filter}
+monitor_speed     = 250000
 
 #
 # ATmega1280
 #
 [env:megaatmega1280]
-platform      = atmelavr
-framework     = arduino
-board         = megaatmega1280
-build_flags   = ${common.build_flags}
-board_f_cpu   = 16000000L
-lib_deps      = ${common.lib_deps}
-src_filter    = ${common.default_src_filter}
-monitor_speed = 250000
+platform          = atmelavr
+framework         = arduino
+board             = megaatmega1280
+build_flags       = ${common.build_flags}
+board_build.f_cpu = 16000000L
+lib_deps          = ${common.lib_deps}
+src_filter        = ${common.default_src_filter}
+monitor_speed     = 250000
 
 #
 # AT90USB1286 boards using CDC bootloader
 # NXP LPC1768 ARM Cortex-M3
 #
 [env:LPC1768]
-platform        = nxplpc
-board           = lpc1768
-board_f_cpu     = 100000000L
-build_flags     = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+platform          = nxplpc
+board             = lpc1768
+board_build.f_cpu = 100000000L
+build_flags       = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
   ${common.build_flags}
   -DU8G_HAL_LINKS
-src_build_flags = -Wall
-build_unflags   = -Wall
-lib_ldf_mode    = off
-lib_extra_dirs  = frameworks
-lib_deps        = CMSIS-LPC1768
+src_build_flags   = -Wall
+build_unflags     = -Wall
+lib_ldf_mode      = off
+lib_extra_dirs    = frameworks
+lib_deps          = CMSIS-LPC1768
   https://github.com/MarlinFirmware/U8glib-HAL/archive/dev.zip
   TMC2130Stepper@>=2.2.1
-extra_scripts   = Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py, Marlin/src/HAL/HAL_LPC1768/upload_extra_script.py
-src_filter      = ${common.default_src_filter}
-monitor_speed   = 250000
+extra_scripts     = Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py, Marlin/src/HAL/HAL_LPC1768/upload_extra_script.py
+src_filter        = ${common.default_src_filter}
+monitor_speed     = 250000
 
 #
 # LPC1768 (for debugging and development)
 #
 [env:LPC1768_debug_and_upload]
 # Segger JLink
-platform       = nxplpc
-#framework     = mbed
-board          = lpc1768
-board_f_cpu    = 100000000L
-build_flags    = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+platform          = nxplpc
+#framework        = mbed
+board             = lpc1768
+board_build.f_cpu = 100000000L
+build_flags       = !python Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
   ${common.build_flags}
   -DU8G_HAL_LINKS
-lib_ldf_mode   = off
-lib_extra_dirs = frameworks
-lib_deps       = CMSIS-LPC1768
+lib_ldf_mode      = off
+lib_extra_dirs    = frameworks
+lib_deps          = CMSIS-LPC1768
   https://github.com/MarlinFirmware/U8glib-HAL/archive/dev.zip
-src_filter     = ${common.default_src_filter}
-extra_scripts  =  Marlin/src/HAL/HAL_LPC1768/debug_extra_script.py, Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
-monitor_speed  = 250000
-debug_tool     = custom
-debug_server   =
+src_filter        = ${common.default_src_filter}
+extra_scripts     =  Marlin/src/HAL/HAL_LPC1768/debug_extra_script.py, Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py
+monitor_speed     = 250000
+debug_tool        = custom
+debug_server      =
   C:\Program Files (x86)\SEGGER\JLink_V618d\JLinkGDBServerCL.exe
   -select USB
   -port 2331
 # RAMBo
 #
 [env:rambo]
-platform      = atmelavr
-framework     = arduino
-board         = reprap_rambo
-build_flags   = ${common.build_flags}
-board_f_cpu   = 16000000L
-lib_deps      = ${common.lib_deps}
-src_filter    = ${common.default_src_filter}
-monitor_speed = 250000
+platform          = atmelavr
+framework         = arduino
+board             = reprap_rambo
+build_flags       = ${common.build_flags}
+board_build.f_cpu = 16000000L
+lib_deps          = ${common.lib_deps}
+src_filter        = ${common.default_src_filter}
+monitor_speed     = 250000
 
 #
 # Sanguinololu (ATmega644p)
 # Teensy++ 2.0
 #
 [env:teensy20]
-platform      = teensy
-framework     = arduino
-board         = teensy20pp
-build_flags   = ${common.build_flags}
-#board_f_cpu  = 20000000L     ; Bug in Arduino framework disallows boards running at 20Mhz
-lib_deps      = ${common.lib_deps}
-lib_ldf_mode  = deep+
-src_filter    = ${common.default_src_filter}
-monitor_speed = 250000
+platform          = teensy
+framework         = arduino
+board             = teensy20pp
+build_flags       = ${common.build_flags}
+#board_build.f_cpu = 20000000L     ; Bug in Arduino framework disallows boards running at 20Mhz
+lib_deps          = ${common.lib_deps}
+lib_ldf_mode      = deep+
+src_filter        = ${common.default_src_filter}
+monitor_speed     = 250000
 
 #
 # Teensy 3.5 / 3.6 (ARM Cortex-M4)
 [env:malyanm200]
 platform    = ststm32
 framework   = arduino
-board = malyanM200
+board       = malyanM200
 build_flags = !python Marlin/src/HAL/HAL_STM32F1/stm32f1_flag_script.py -DMCU_STM32F103CB -D __STM32F1__=1 -std=c++1y -D MOTHERBOARD="BOARD_MALYAN_M200" -DSERIAL_USB -ffunction-sections -fdata-sections -Wl,--gc-sections
-src_filter = ${common.default_src_filter}
+src_filter  = ${common.default_src_filter}
 #-<frameworks>
-lib_ignore =
+lib_ignore  =
   U8glib
   LiquidCrystal_I2C
   LiquidCrystal