output: Check for fwrite_unlocked

This commit creates a macro for fwrite_unlocked which is probed during
configuration time.

configure.ac

@@ -245,6 +245,8 @@
     AC_CHECK_FUNCS([gettimeofday clock_gettime utime strptime tzset localtime_r])
     AC_CHECK_FUNCS([socket setenv select putenv dup2 endgrent endpwent atexit munmap])
 
+    AC_CHECK_FUNCS([fwrite_unlocked])
+
     AC_CHECK_DECL([getrandom],
         AC_DEFINE([HAVE_GETRANDOM], [1], [Use getrandom]),
         [], [

src/suricata-common.h

@@ -520,6 +520,11 @@ size_t strlcpy(char *dst, const char *src, size_t siz);
 char *strptime(const char * __restrict, const char * __restrict, struct tm * __restrict);
 #endif
 
+#ifndef HAVE_FWRITE_UNLOCKED
+#define SCFwriteUnlocked    fwrite
+#else
+#define SCFwriteUnlocked    fwrite_unlocked
+#endif
 extern int coverage_unittests;
 extern int g_ut_modules;
 extern int g_ut_covered;