Make mutexes init in DATA, not ((counstructor)) (#645)

There was a race condition in making mutexes that were only init in
an __attribute((constructor)) code block.  For example, a global
object might do a `malloc` in its constructor which would depend on
the malloc mutex...which may not yet have been initted.

Make them initted in the .data section, instead, which is guaranteed
good before any global constructors are called.

Author: earlephilhower

cores/rp2040/lock.cpp renamed to cores/rp2040/lock.c

@@ -25,28 +25,22 @@
 #include <pico/mutex.h>
 #include <sys/lock.h>
 
-recursive_mutex_t __lock___sinit_recursive_mutex;
-recursive_mutex_t __lock___sfp_recursive_mutex;
-recursive_mutex_t __lock___atexit_recursive_mutex;
-mutex_t __lock___at_quick_exit_mutex;
-recursive_mutex_t __lock___malloc_recursive_mutex;
-recursive_mutex_t __lock___env_recursive_mutex;
-mutex_t __lock___tz_mutex;
-mutex_t __lock___dd_hash_mutex;
-mutex_t __lock___arc4random_mutex;
-
-
-__attribute__((constructor)) void __init_all_newlib_mutexes() {
-    recursive_mutex_init(&__lock___sinit_recursive_mutex);
-    recursive_mutex_init(&__lock___sfp_recursive_mutex);
-    recursive_mutex_init(&__lock___atexit_recursive_mutex);
-    mutex_init(&__lock___at_quick_exit_mutex);
-    recursive_mutex_init(&__lock___malloc_recursive_mutex);
-    recursive_mutex_init(&__lock___env_recursive_mutex);
-    mutex_init(&__lock___tz_mutex);
-    mutex_init(&__lock___dd_hash_mutex);
-    mutex_init(&__lock___arc4random_mutex);
-}
+// HACK ALERT
+// Pico-SDK defines mutex which can be at global scope, but when the auto_init_
+// macros are used they are defined as static.  Newlib needs global access to
+// these mutextes, so instead of hacking pico-sdk just make "static" a no-op.
+
+#define static
+auto_init_recursive_mutex(__lock___sinit_recursive_mutex);
+auto_init_recursive_mutex(__lock___sfp_recursive_mutex);
+auto_init_recursive_mutex(__lock___atexit_recursive_mutex);
+auto_init_mutex(__lock___at_quick_exit_mutex);
+auto_init_recursive_mutex(__lock___malloc_recursive_mutex);
+auto_init_recursive_mutex(__lock___env_recursive_mutex);
+auto_init_mutex(__lock___tz_mutex);
+auto_init_mutex(__lock___dd_hash_mutex);
+auto_init_mutex(__lock___arc4random_mutex);
+#undef static
 
 void __retarget_lock_init(_LOCK_T *lock) {
     mutex_init((mutex_t*) lock);