Create replacement endian.h if needed.

Remove #ifdef HAVE_ENDIAN_H wrapper.  ok djm@

configure.ac

@@ -457,7 +457,6 @@ AC_CHECK_HEADERS([ \
 	crypt.h \
 	crypto/sha2.h \
 	dirent.h \
-	endian.h \
 	elf.h \
 	err.h \
 	features.h \
@@ -529,6 +528,7 @@ AC_CHECK_HEADERS([ \
 # '#ifdef HAVE_FOO_H'.  If we create any such headers, add the path to includes.
 compatincludes=no
 AC_CHECK_HEADERS([ \
+    endian.h \
     ifaddrs.h \
     libgen.h \
     paths.h \

kexmlkem768x25519.c

@@ -32,9 +32,7 @@
 #include <stdbool.h>
 #include <string.h>
 #include <signal.h>
-#ifdef HAVE_ENDIAN_H
-# include <endian.h>
-#endif
+#include <endian.h>
 
 #include "sshkey.h"
 #include "kex.h"