Fix clang -Wcompound-token-split-by-macro warning in ruby.h

Building certain ruby gem native extensions (such as thrift), with clang
12.0.0 or later fails, because they have -Werror in their CFLAGS,
resulting in complaints about the expansion of the `rb_intern()` macro:

```
current directory: /wrkdirs/usr/ports/devel/rubygem-thrift/work/stage/usr/local/lib/ruby/gems/2.7/gems/thrift-0.14.0/ext
make "DESTDIR="
compiling binary_protocol_accelerated.c
binary_protocol_accelerated.c:404:68: error: '(' and '{' tokens introducing statement expression appear in different macro expansion contexts [-Werror,-Wcompound-token-split-by-macro]
  VALUE thrift_binary_protocol_class = rb_const_get(thrift_module, rb_intern("BinaryProtocol"));
                                                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/ruby-2.7/ruby/ruby.h:1847:23: note: expanded from macro 'rb_intern'
        __extension__ (RUBY_CONST_ID_CACHE((ID), (str))) : \
                      ^
binary_protocol_accelerated.c:404:68: note: '{' token is here
  VALUE thrift_binary_protocol_class = rb_const_get(thrift_module, rb_intern("BinaryProtocol"));
                                                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/ruby-2.7/ruby/ruby.h:1847:24: note: expanded from macro 'rb_intern'
        __extension__ (RUBY_CONST_ID_CACHE((ID), (str))) : \
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/ruby-2.7/ruby/ruby.h:1832:5: note: expanded from macro 'RUBY_CONST_ID_CACHE'
    {                                                   \
    ^
```

Part of the `rb_intern()` macro expands to `(RUBY_CONST_ID_CACHE((ID),
(str)))`, and in turn `RUBY_CONST_ID_CACHE()` expands to a brace
enclosed compound statement. The intended effect is to get a gcc
statement expression, which is normally delimited by `({ ... })`.

However, clang 12.0.0 and later have a warning enabled by default, about
pasting together the `(` and `{` tokens via different macros (see
<https://github.com/llvm/llvm-project/commit/0e00a95b4fad5e72851de012d3a0b2c2d01f8685>).

To work around this warning:
* Add `RUBY_CONST_ID_CACHE_NB()` (i.e. no-brace) which contains the code
  itself, without any braces
* `RUBY_CONST_ID_CACHE()` which uses `RUBY_CONST_ID_CACHE_NB()`, but
   puts braces around it (so no existing code using this macro breaks)
* Finally, change `rb_intern()` so the `__extension__` directly creates
  a gcc statement expression, using the `RUBY_CONST_ID_CACHE_NB()` macro

0 files changed, 0 insertions, 0 deletions