add HAVE_STRNSTR

configure

@@ -474,6 +474,27 @@ else
 fi
 rm -f _$func.c _$func
 
+#
+# Check for strnstr().
+func=strnstr
+printf "Checking for $func() ... "
+cat <<EOF > _$func.c
+#include <string.h>
+int main(void) {
+	const char big[] = "foo";
+	const char little[] = "f";
+	strnstr(big, little, 3);
+	return 0;
+}
+EOF
+if $XCC _$func.c -o _$func 2>/dev/null; then
+	echo yes.
+	echo "CPPFLAGS +=	-DHAVE_STRNSTR" >>$CONFIG_MK
+else
+	echo no.
+fi
+rm -f _$func.c _$func
+
 #
 # Check for humanize_number().
 func=humanize_number

lib/fetch/common.c

@@ -444,6 +444,8 @@ fetch_cache_put(conn_t *conn, int (*closecb)(conn_t *))
 
 
 #ifdef WITH_SSL
+
+#ifndef HAVE_STRNSTR
 /*
  * Find the first occurrence of find in s, where the search is limited to the
  * first slen characters of s.
@@ -468,6 +470,7 @@ strnstr(const char *s, const char *find, size_t slen)
 	}
 	return ((char *)__UNCONST(s));
 }
+#endif
 
 /*
  * Convert characters A-Z to lowercase (intentionally avoid any locale