Use toolchain-pico

platform.json

@@ -31,6 +31,12 @@
       "owner": "platformio",
       "version": "~1.90201.0"
     },
+    "toolchain-pico": {
+      "type": "toolchain", 
+      "optional": true,
+      "owner": "maxgerhardt",
+      "version": "~5.100300.0"
+    },
     "framework-arduino-mbed": {
       "type": "framework",
       "optional": true,

platform.py

@@ -40,6 +40,8 @@ class RaspberrypiPlatform(PlatformBase):
             elif build_core == "earlephilhower":
                 self.frameworks["arduino"]["package"] = "framework-arduinopico"
                 self.packages["framework-arduino-mbed"]["optional"] = True
+                self.packages.pop("toolchain-gccarmnoneeabi", None)
+                self.packages["toolchain-pico"]["optional"] = False                
             else:
                 sys.stderr.write(
                     "Error! Unknown build.core value '%s'. Don't know which Arduino core package to use." % build_core)