headers: Use the right windows specific arm instruction for __debugbreak()

The udf arm instruction has a platform specific meaning; on Windows
udf #0xfe is mapped to an exception with STATUS_BREAKPOINT. (The
previous instruction form does stop execution in a debugger, but
continuing might not be possible, but with udf #0xfe it is possible
to continue after stopping.)

Signed-off-by: Martin Storsjö <martin@martin.st>

mingw-w64-headers/crt/_mingw.h.in

diff --git a/mingw-w64-headers/crt/_mingw.h.in b/mingw-w64-headers/crt/_mingw.h.in
index 89b1d25..b7fb99f 100644
--- a/mingw-w64-headers/crt/_mingw.h.in
+++ b/mingw-w64-headers/crt/_mingw.h.in
@@ -583,7 +583,7 @@
 #if defined(__i386__) || defined(__x86_64__)
   __asm__ __volatile__("int {$}3":);
 #elif defined(__arm__)
-  __asm__ __volatile__("udf #1");
+  __asm__ __volatile__("udf #0xfe");
 #elif defined(__aarch64__)
   __asm__ __volatile__("brk #0xf000");
 #else