%Id is a glibc extension. The "I" character is used elsewhere in other
extensions too. For example, %I is a Microsoft extension for printing
size_t. Although undocumented on Darwin, that platform's libc emulates
the Microsoft extension.

If %I is interpreted as size_t, then the code is likely to crash on
platforms where int and size_t are different widths, such as 64-bit OSX.

This adds a configure-time check for %Id. When it's not supported, then
the provided sample program will error out when compiled with -Werror. If
not supported then we simply print %d since I don't believe the
alternative representation flag has any other equivalent on other
platforms.

https://bugzilla.gnome.org/show_bug.cgi?id=773297