Expose defines and rbconfig values to dependent crates

[ianks]

This PR makes it so conf values from bindings.rs are exposed to upstream packages. This makes this like env.var("DEP_RB_DEFINES_USE_FLONUM") possible. You can always see everything rb-sys exposes by setting the RB_SYS_DEBUG_BUILD=1 environment variable when building your crate.

Here is a list of the new exposed values:

cargo:defines_have_rb_data_type_t_function="true"
cargo:defines_have_rb_data_type_t_parent="true"
cargo:defines_have_rb_define_alloc_func="true"
cargo:defines_have_rb_ext_ractor_safe="true"
cargo:defines_have_rb_fd_init="true"
cargo:defines_have_rb_io_t="true"
cargo:defines_have_rb_reg_new_str="true"
cargo:defines_have_rb_scan_args_optional_hash="true"
cargo:defines_have_ruby_atomic_h="true"
cargo:defines_have_ruby_debug_h="true"
cargo:defines_have_ruby_defines_h="true"
cargo:defines_have_ruby_encoding_h="true"
cargo:defines_have_ruby_fiber_scheduler_h="true"
cargo:defines_have_ruby_intern_h="true"
cargo:defines_have_ruby_io_h="true"
cargo:defines_have_ruby_memory_view_h="true"
cargo:defines_have_ruby_missing_h="true"
cargo:defines_have_ruby_onigmo_h="true"
cargo:defines_have_ruby_oniguruma_h="true"
cargo:defines_have_ruby_ractor_h="true"
cargo:defines_have_ruby_random_h="true"
cargo:defines_have_ruby_re_h="true"
cargo:defines_have_ruby_regex_h="true"
cargo:defines_have_ruby_ruby_h="true"
cargo:defines_have_ruby_st_h="true"
cargo:defines_have_ruby_thread_h="true"
cargo:defines_have_ruby_thread_native_h="true"
cargo:defines_have_ruby_util_h="true"
cargo:defines_have_ruby_version_h="true"
cargo:defines_have_ruby_vm_h="true"
cargo:defines_use_flonum="true"
cargo:defines_use_gc_malloc_obj_info_details="false"
cargo:defines_use_mjit="true"
cargo:defines_use_rgengc="true"
cargo:defines_use_rgengc_logging_wb_unprotect="false"
cargo:defines_use_rincgc="true"
cargo:defines_use_rvargc="false"
cargo:defines_use_symbol_as_method_name="true"
cargo:defines_use_transient_heap="true"
cargo:defines_use_unaligned_member_access="true"

This PR also exposes all rbconfig values available, which can be accessed like: env.var("DEP_RB_RBCONFIG_MY_KEY")

cargo:rbconfig_sitearchincludedir="/Users/ianks/.rubies/3.1.2/include/arm64-darwin21"
...

[matsadler]

Awesome! Looks good