Update platform-specific defaults

source/m3_config_platforms.h

@@ -76,6 +76,8 @@
 #   define M3_ARCH "mips"
 #  elif defined(__xtensa__)
 #   define M3_ARCH "xtensa"
+#  elif defined(__riscv)
+#   define M3_ARCH "riscv"
 #  elif defined(__AVR__)
 #   define M3_ARCH "avr"
 #  endif
@@ -197,7 +199,7 @@ typedef int8_t          i8;
  * Platform-specific defaults
  */
 
-# if defined(ARDUINO) || defined(PARTICLE) || defined(__MBED__) || defined(ESP8266) || defined(ESP32) || defined(BLUE_PILL) || defined(WM_W600) || defined(FOMU)
+# if defined(ARDUINO) || defined(PARTICLE) || defined(PLATFORMIO) || defined(__MBED__) || defined(ESP8266) || defined(ESP32) || defined(BLUE_PILL) || defined(WM_W600) || defined(FOMU)
 #  ifndef d_m3LogOutput
 #    define d_m3LogOutput                       false
 #  endif