Clang16 will not allow using undeclared library functions by default.
This imports ctype.h into that check so isdigit() can be used without errors.

Bug: https://bugs.gentoo.org/879737

PR upstream: https://github.com/deanproxy/eMail/pull/63

Signed-off-by: Pascal Jäger <pascal.jaeger@leimstift.de>

--- a/check_strftime.sh
+++ b/check_strftime.sh
@@ -14,6 +14,7 @@ cat << EOF > /tmp/strftime_try.c
 #include <stdlib.h>
 #include <time.h>
 #include <sys/time.h>
+#include <ctype.h>
 
 int
 main (void)