Add errno information to some not implemented syscalls. See https://sourceware.org/newlib/libc.html#Syscalls

newlib/libc/sys/sh3eb/syscalls.c

@@ -1,4 +1,5 @@
 #include <_ansi.h>
+#include <sys/errno.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/time.h>
@@ -43,6 +44,7 @@ _close (int file)
 int
 _link (char *old, char *new)
 {
+  errno = EMLINK;
   return -1;
 }
 
@@ -76,6 +78,7 @@ _creat (const char *path,
 int
 _unlink ()
 {
+  errno = ENOENT;
   return -1;
 }
 
@@ -99,6 +102,7 @@ _exit (n)
 
 _kill (n, m)
 {
+  errno = EINVAL;
   return -1;
 }
 
@@ -141,6 +145,7 @@ _utime (path, times)
 int
 _fork ()
 {
+  errno = EAGAIN;
   return -1;
 }
 
@@ -148,12 +153,14 @@ int
 _wait (statusp)
      int *statusp;
 {
+  errno = ECHILD;
   return -1;
 }
 
 int
 _execve (const char *path, char *const argv[], char *const envp[])
 {
+  errno = ENOMEM;
   return -1;
 }