Fix linker errors with latest Swift toolchain snapshot

The main-snapshot-2026-01-09 toolchain changed swift_allocObject to call
posix_memalign instead of malloc, and pulls in additional newlib symbols.
The previous Swift posix_memalign stub was being dead-stripped by the
whole-module optimizer since nothing in Swift code references it directly.

- Move posix_memalign to C in setup.c where it won't be dead-stripped
- Add bare-metal stubs for newlib syscalls (_getentropy/getentropy,
  _kill, _getpid, _close, _lseek, _read, _write, _fstat, _isatty)
- Add -DTARGET_PLAYDATE=1 to device toolset to match the SDK's own build
  system (common.mk), enabling the correct #if TARGET_PLAYDATE branch
- Make pdrealloc non-static so Xkpd CLodePNG can reference it
- Update .swift-version to main-snapshot-2026-01-09

Author: finnvoor

.swift-version

@@ -1 +1 @@
-main-snapshot-2025-05-25
+main-snapshot-2026-01-09

Examples/FlappySwift/Package.resolved

@@ -1,12 +1,13 @@
 #ifdef TARGET_PLAYDATE
-  extern void* pdrealloc(void* ptr, size_t size);
-  void* lodepng_malloc(size_t size) { return pdrealloc(NULL, size); }
-  void* lodepng_realloc(void* ptr, size_t size) { return pdrealloc(ptr, size); }
-  void  lodepng_free(void* ptr) { if(ptr) pdrealloc(ptr, 0); }
+  #include <stddef.h>
+  extern void* malloc(size_t);
+  extern void* realloc(void*, size_t);
+  extern void  free(void*);
 #else
   #include <stdlib.h>
-  void* lodepng_malloc(size_t size) { return malloc(size); }
-  void* lodepng_realloc(void* ptr, size_t size) { return realloc(ptr, size); }
-  void  lodepng_free(void* ptr) { free(ptr); }
 #endif
 
+void* lodepng_malloc(size_t size) { return malloc(size); }
+void* lodepng_realloc(void* ptr, size_t size) { return realloc(ptr, size); }
+void  lodepng_free(void* ptr) { free(ptr); }
+

Examples/Pong/Package.resolved

@@ -5,7 +5,7 @@ typedef int (PDEventHandler)(PlaydateAPI* playdate, PDSystemEvent event, uint32_
 
 extern PDEventHandler eventHandler;
 
-static void* (*pdrealloc)(void* ptr, size_t size);
+void* (*pdrealloc)(void* ptr, size_t size);
 
 int eventHandlerShim(PlaydateAPI* playdate, PDSystemEvent event, uint32_t arg)
 {
@@ -21,6 +21,46 @@ void* _malloc_r(struct _reent* _REENT, size_t nbytes) { return pdrealloc(NULL,nb
 void* _realloc_r(struct _reent* _REENT, void* ptr, size_t nbytes) { return pdrealloc(ptr,nbytes); }
 void _free_r(struct _reent* _REENT, void* ptr ) { if ( ptr != NULL ) pdrealloc(ptr,0); }
 
+int getentropy(void *buffer, size_t length) {
+    return -1;
+}
+
+int _getentropy(void *buffer, size_t length) {
+    return -1;
+}
+
+int _kill(int pid, int sig) {
+    return -1;
+}
+
+int _getpid(void) {
+    return 1;
+}
+
+int _close(int fd) {
+    return -1;
+}
+
+int _lseek(int fd, int offset, int whence) {
+    return -1;
+}
+
+int _read(int fd, void *buf, int count) {
+    return -1;
+}
+
+int _write(int fd, const void *buf, int count) {
+    return -1;
+}
+
+int _fstat(int fd, void *buf) {
+    return -1;
+}
+
+int _isatty(int fd) {
+    return 0;
+}
+
 #else
 
 void* malloc(size_t nbytes) { return pdrealloc(NULL,nbytes); }
@@ -29,4 +69,11 @@ void  free(void* ptr ) { if ( ptr != NULL ) pdrealloc(ptr,0); }
 
 #endif
 
+int posix_memalign(void **memptr, size_t alignment, size_t size) {
+    void *ptr = pdrealloc(NULL, size);
+    if (!ptr) return 12; // ENOMEM
+    *memptr = ptr;
+    return 0;
+}
+
 void *swift_coroFrameAlloc(size_t bytes, unsigned long long typeId) { return pdrealloc(NULL,bytes); }

Examples/Xkpd/Package.resolved

@@ -41,21 +41,6 @@ public enum Playdate {
     private nonisolated(unsafe) static var _playdateAPI: PlaydateAPI?
 }
 
-/// Implement `posix_memalign(3)`, which is required by the Embedded Swift runtime but is
-/// not provided by the Playdate C library.
-@_documentation(visibility: internal)
-@_cdecl("posix_memalign") public func posix_memalign(
-    _ memptr: UnsafeMutablePointer<UnsafeMutableRawPointer?>,
-    _ alignment: Int,
-    _ size: Int
-) -> CInt {
-    guard let allocation = malloc(Int(size + alignment - 1)) else { fatalError() }
-    let misalignment = Int(bitPattern: allocation) % alignment
-    precondition(misalignment == 0)
-    memptr.pointee = allocation
-    return 0
-}
-
 /// Implement `arc4random_buf` which is required by the Embedded Swift runtime for Hashable, Set, Dictionary,
 /// and random-number generating APIs but is not provided by the Playdate C library.
 @_documentation(visibility: internal)

Examples/Xkpd/Sources/CLodePNG/setup.c

@@ -15,6 +15,7 @@
 			"-mfloat-abi=hard",
 			"-mfpu=fpv5-sp-d16",
 			"-D__FPU_USED=1",
+			"-DTARGET_PLAYDATE=1",
 
 			"-falign-functions=16",
 			"-fshort-enums"