tst-rec-dlopen: Fix build fail due to missing inclusion of string.h

on S390, I get a compile error for dlfcn/tst-rec-dlopen.c:
tst-rec-dlopen.c: In function ‘malloc’:
tst-rec-dlopen.c:101:4: error: implicit declaration of function ‘strlen’ [-Werror=implicit-function-declaration]
    (void) write (STDOUT_FILENO, message, strlen (message));
    ^
tst-rec-dlopen.c:101:42: error: incompatible implicit declaration of built-in function ‘strlen’ [-Werror]
    (void) write (STDOUT_FILENO, message, strlen (message));
                                          ^
tst-rec-dlopen.c:112:42: error: incompatible implicit declaration of built-in function ‘strlen’ [-Werror]
    (void) write (STDOUT_FILENO, message, strlen (message));
                                          ^

This patch adds the missing "#include <string.h>" for strlen.

ChangeLog:

	* dlfcn/tst-rec-dlopen.c: Include string.h.

1 files changed, 1 insertions, 0 deletions

diff --git a/dlfcn/tst-rec-dlopen.c b/dlfcn/tst-rec-dlopen.c
index 07e0cc467a..0269851b63 100644
--- a/dlfcn/tst-rec-dlopen.c
+++ b/dlfcn/tst-rec-dlopen.c
@@ -23,6 +23,7 @@
 #include <stdalign.h>
 #include <sys/mman.h>
 #include <unistd.h>
+#include <string.h>
 
 #define DSO "moddummy1.so"
 #define FUNC "dummy1"