Fix assembler flags (#2255)

An oversight in the order of updating the ASFLAGS with a copy of the CCFLAGS (see line 110) and then updating the CCFLAGS (without resyncing the ASFLAGS) leads to a fatal compilation error in the Adafruit PicoDVI library, in which `tmds_encode.S` fails to find the `pico/config.h` include file. This fix updates the ASFLAGS manually after changing the CCFLAGS so that they're equal again, and the library can be compiled.

tools/platformio-build.py

@@ -190,7 +190,10 @@ else:
         "-iprefix" + os.path.join(FRAMEWORK_DIR),
         "@%s" % os.path.join(FRAMEWORK_DIR, "lib", "platform_inc.txt")
     ])
-
+    env.Append(ASFLAGS=[
+        "-iprefix" + os.path.join(FRAMEWORK_DIR),
+        "@%s" % os.path.join(FRAMEWORK_DIR, "lib", "platform_inc.txt")
+    ])
 
 def configure_usb_flags(cpp_defines):
     if "USE_TINYUSB" in cpp_defines: