Update pico-sdk and bazelify it

This borrows heavily from work that Austin did to initially get this
stuff working.

Merge commit 'a1fdcd85e25a8a2b1e3ca5bc31e45bedf9e58266' into HEAD

Signed-off-by: Ravago Jones <ravagojones@gmail.com>
Change-Id: Id47d383bd5fb46664083b365890fd7bad5786c1f
diff --git a/third_party/pico-sdk/hex.bzl b/third_party/pico-sdk/hex.bzl
index 31c951c..b668ce0 100644
--- a/third_party/pico-sdk/hex.bzl
+++ b/third_party/pico-sdk/hex.bzl
@@ -23,3 +23,17 @@
             "//third_party/pico-sdk/tools/elf2uf2",
         ],
     )
+
+def pioasm(name, src, out, target_compatible_with = None):
+    native.genrule(
+        name = name,
+        srcs = [src],
+        outs = [out],
+        cmd = "$(location //third_party/pico-sdk/tools/pioasm) -o c-sdk $< $@",
+        executable = True,
+        output_to_bindir = True,
+        target_compatible_with = target_compatible_with,
+        tools = [
+            "//third_party/pico-sdk/tools/pioasm",
+        ],
+    )