To support compiling with libmongocrypt, we will add a new --with-libmongocrypt configure switch. The switch has the following values:

• auto (default value): compile with libmongocrypt if found, ignore if not found;
• yes: compile with libmongocrypt if found, abort with error if not found;
• no: compile without libmongocrypt.

To compile with libmongocrypt, we will bundle libmongocrypt alongside libbson and libmongoc. When determining whether to use a system libmongocrypt or the bundled version, we will look to the --with-libbson switch:

• With yes, we will check for a system libmongocrypt and handle a missing libmongocrypt according to the list above;
• With no, we will use bundled libmongocrypt.