fix pico_set_printf_implementation(TARGET compiler) (#593)

Author: kilograham

src/rp2_common/pico_runtime/runtime.c

@@ -20,7 +20,13 @@
 
 #include "pico/mutex.h"
 #include "pico/time.h"
+
+#if LIB_PICO_PRINTF_PICO
 #include "pico/printf.h"
+#else
+#define weak_raw_printf printf
+#define weak_raw_vprintf vprintf
+#endif
 
 #if PICO_ENTER_USB_BOOT_ON_EXIT
 #include "pico/bootrom.h"

src/rp2_common/pico_stdio/stdio.c

@@ -10,7 +10,9 @@
 
 #include "pico.h"
 #include "pico/mutex.h"
+#if LIB_PICO_PRINTF_PICO
 #include "pico/printf.h"
+#endif
 #include "pico/stdio.h"
 #include "pico/stdio/driver.h"
 #include "pico/time.h"