deps: Add ARM64 definitions in w32-pthreads

Update w32-pthreads/context.h to include definitions for _M_ARM and
_M_ARM64 in addition to existing ARM definitions.

deps/w32-pthreads/context.h

@@ -63,7 +63,7 @@
 #define PTW32_PROGCTR(Context)  ((Context).Rip)
 #endif
 
-#if defined(_ARM_) || defined(ARM)
+#if defined(_ARM_) || defined(ARM) || defined(_M_ARM) || defined(_M_ARM64)
 #define PTW32_PROGCTR(Context)  ((Context).Pc)
 #endif