Let libmaple accept RX/TX_BUFFER_SIZE (#21177)

buildroot/share/PlatformIO/scripts/fix_framework_weakness.py

         print("Done patching exception handler")
 
     print("Libmaple modified and ready for post mortem debugging")
+
+rxBuf = env["MARLIN_FEATURES"]["RX_BUFFER_SIZE"] if "RX_BUFFER_SIZE" in env["MARLIN_FEATURES"] else "0"
+txBuf = env["MARLIN_FEATURES"]["TX_BUFFER_SIZE"] if "TX_BUFFER_SIZE" in env["MARLIN_FEATURES"] else "0"
+if int(rxBuf) < 64:
+	rxBuf = "64"
+
+if int(txBuf) < 64:
+	txBuf = "64"
+
+build_flags = env.get('BUILD_FLAGS')
+build_flags.append("-DUSART_RX_BUF_SIZE=" + rxBuf + " -DUSART_TX_BUF_SIZE=" + txBuf)
+env.Replace(BUILD_FLAGS=build_flags)

platformio.ini

   SoftwareSerialM
 platform_packages = tool-stm32duino
 extra_scripts     = ${common.extra_scripts}
-  buildroot/share/PlatformIO/scripts/fix_framework_weakness.py
+  pre:buildroot/share/PlatformIO/scripts/fix_framework_weakness.py
 
 #
 # STM32F103RC
 [env:STM32F103RC_fysetc]
 platform          = ${common_stm32f1.platform}
 extends           = env:STM32F103RC
-extra_scripts     = ${common.extra_scripts}
+extra_scripts     = ${common_stm32f1.extra_scripts}
   buildroot/share/PlatformIO/scripts/STM32F103RC_fysetc.py
 build_flags       = ${common_stm32f1.build_flags} -DDEBUG_LEVEL=0
 lib_ldf_mode      = chain
 [env:STM32F103RC_btt]
 platform          = ${common_stm32f1.platform}
 extends           = env:STM32F103RC
-extra_scripts     = ${common.extra_scripts}
+extra_scripts     = ${common_stm32f1.extra_scripts}
   buildroot/share/PlatformIO/scripts/STM32F103RC_SKR_MINI.py
 build_flags       = ${common_stm32f1.build_flags}
   -DDEBUG_LEVEL=0 -DSS_TIMER=4
 [env:STM32F103RE_btt]
 platform          = ${common_stm32f1.platform}
 extends           = env:STM32F103RE
-extra_scripts     = ${common.extra_scripts}
+extra_scripts     = ${common_stm32f1.extra_scripts}
   buildroot/share/PlatformIO/scripts/STM32F103RE_SKR_E3_DIP.py
 build_flags       = ${common_stm32f1.build_flags} -DDEBUG_LEVEL=0 -DSS_TIMER=4
 debug_tool        = stlink
 platform        = ${common_stm32f1.platform}
 extends         = common_stm32f1
 board           = genericSTM32F103VE
-extra_scripts   = ${common.extra_scripts}
+extra_scripts   = ${common_stm32f1.extra_scripts}
   buildroot/share/PlatformIO/scripts/mks_robin_nano35.py
 build_flags     = ${common_stm32f1.build_flags}
   -DMCU_STM32F103VE -DSS_TIMER=4
 extends       = common_stm32f1
 board         = genericSTM32F103RC
 platform_packages = tool-stm32duino
-extra_scripts = ${common.extra_scripts}
+extra_scripts = ${common_stm32f1.extra_scripts}
   buildroot/share/PlatformIO/scripts/mks_robin_e3.py
 build_flags   = ${common_stm32f1.build_flags}
   -DDEBUG_LEVEL=0 -DSS_TIMER=4