Handle systems missing <sys/cdefs.h>

This is a non-portable header, and we cannot expect it to be provided by
the system libc (e.g. musl). We just need and rely on declaration that
we have defined ourselves in our own <bsd/sys/cdefs.h>. So we switch to
only ever assume that.

Fixes: https://bugs.freedesktop.org/105281

include/bsd/libutil.h

@@ -40,7 +40,11 @@
 #define LIBBSD_LIBUTIL_H
 
 #include <features.h>
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/types.h>
 #include <stdint.h>
 #include <stdio.h>

include/bsd/md5.h

@@ -27,7 +27,11 @@ typedef struct MD5Context {
 	uint8_t buffer[MD5_BLOCK_LENGTH];	/* input buffer */
 } MD5_CTX;
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/types.h>
 
 __BEGIN_DECLS

include/bsd/nlist.h

@@ -27,7 +27,11 @@
 #ifndef LIBBSD_NLIST_H
 #define LIBBSD_NLIST_H
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 
 struct nlist {
 	union {

include/bsd/readpassphrase.h

@@ -31,7 +31,11 @@
 #define RPP_SEVENBIT    0x10		/* Strip the high bit from input. */
 #define RPP_STDIN       0x20		/* Read from stdin, not /dev/tty */
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/types.h>
 
 __BEGIN_DECLS

include/bsd/stdlib.h

@@ -42,7 +42,11 @@
 #ifndef LIBBSD_STDLIB_H
 #define LIBBSD_STDLIB_H
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/stat.h>
 #include <stdint.h>
 

include/bsd/string.h

@@ -33,7 +33,11 @@
 #ifndef LIBBSD_STRING_H
 #define LIBBSD_STRING_H
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/types.h>
 
 __BEGIN_DECLS

include/bsd/stringlist.h

@@ -31,7 +31,12 @@
 
 #ifndef LIBBSD_STRINGLIST_H
 #define LIBBSD_STRINGLIST_H
+
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/types.h>
 
 /*

include/bsd/sys/queue.h

@@ -33,7 +33,11 @@
 #ifndef LIBBSD_SYS_QUEUE_H
 #define LIBBSD_SYS_QUEUE_H
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 
 /*
  * This file defines four types of data structures: singly-linked lists,

include/bsd/sys/tree.h

@@ -30,7 +30,11 @@
 #ifndef LIBBSD_SYS_TREE_H
 #define LIBBSD_SYS_TREE_H
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 
 /*
  * This file defines data structures for different types of trees:

include/bsd/timeconv.h

@@ -41,7 +41,11 @@
 #ifndef LIBBSD_TIMECONV_H
 #define LIBBSD_TIMECONV_H
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <stdint.h>
 #include <time.h>
 

include/bsd/vis.h

@@ -72,7 +72,11 @@
  */
 #define	UNVIS_END	1	/* no more characters */
 
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 
 __BEGIN_DECLS
 char	*vis(char *, int, int, int);

include/bsd/wchar.h

@@ -40,7 +40,11 @@
 #define LIBBSD_WCHAR_H
 
 #include <stddef.h>
+#ifdef LIBBSD_OVERLAY
 #include <sys/cdefs.h>
+#else
+#include <bsd/sys/cdefs.h>
+#endif
 #include <sys/types.h>
 
 __BEGIN_DECLS