Tweaks to build scripts

buildroot/share/PlatformIO/scripts/SAMD51_grandcentral_m4.py

 
 Import("env")
 
-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"
+mf = env["MARLIN_FEATURES"]
+rxBuf = mf["RX_BUFFER_SIZE"] if "RX_BUFFER_SIZE" in mf else "0"
+txBuf = mf["TX_BUFFER_SIZE"] if "TX_BUFFER_SIZE" in mf else "0"
 
 serialBuf = str(max(int(rxBuf), int(txBuf), 350))
 

buildroot/share/PlatformIO/scripts/common-cxxflags.py

 if env.GetBuildType() == "debug":
 	env['BUILD_DIR'] = '$PROJECT_BUILD_DIR/$PIOENV/debug'
 
-# On some platform, F_CPU is a runtime variable. Since it's used to convert from ns 
-# to CPU cycles, this adds overhead preventing small delay (in the order of less than 
+# On some platform, F_CPU is a runtime variable. Since it's used to convert from ns
+# to CPU cycles, this adds overhead preventing small delay (in the order of less than
 # 30 cycles) to be generated correctly. By using a compile time constant instead
 # the compiler will perform the computation and this overhead will be avoided
 add_cpu_freq()

buildroot/share/PlatformIO/scripts/fix_framework_weakness.py

 
     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"
+mf = env["MARLIN_FEATURES"]
+rxBuf = mf["RX_BUFFER_SIZE"] if "RX_BUFFER_SIZE" in mf else "0"
+txBuf = mf["TX_BUFFER_SIZE"] if "TX_BUFFER_SIZE" in mf else "0"
 if int(rxBuf) < 64:
 	rxBuf = "64"
-
 if int(txBuf) < 64:
 	txBuf = "64"