[llvm][ADT] Use endian.h on managarm

Author: no92

llvm/include/llvm/ADT/bit.h

@@ -30,7 +30,7 @@
 
 #if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__) ||            \
     defined(__Fuchsia__) || defined(__EMSCRIPTEN__) || defined(__NetBSD__) ||  \
-    defined(__OpenBSD__) || defined(__DragonFly__)
+    defined(__OpenBSD__) || defined(__DragonFly__) || defined(__managarm__)
 #include <endian.h>
 #elif defined(_AIX)
 #include <sys/machine.h>