Fix build on some boards due to not directly using printf library

Author: playday3008

build.zig

@@ -14,6 +14,7 @@ const stdio: pico.Stdio = .{
 
 /// Libraries to link
 const link_libs_base = &[_]pico.Lib{
+    pico.api.runtime.pico.printf,
     pico.api.high_level.stdlib,
 };
 

src/sdk.zig

@@ -4,6 +4,7 @@ const pico = @cImport({
 });
 
 pub usingnamespace @cImport({
+    @cInclude("pico/printf.h");
     @cInclude("pico/stdlib.h");
     // Pico W devices use a GPIO on the WIFI chip for the LED,
     // so when building for Pico W, CYW43_WL_GPIO_LED_PIN will be defined