mkmf: Add the extra option `--with-verbose` to enable verbose mode. (#7863)

This commit is to add an extra option to enable verbose mode (V=1) in the
generated `Makefile` at runtime of the Ruby to print compiler command lines by
the commands below when building native extensions. It's possible to enable the
verbose mode by setting the environment variable `MAKEFLAGS="V=1"`[1]
implemented in GNU make. However, I wanted to make a consistent user-interface
not depending on the specific make's implementation.

```
$ ruby /path/to/extconf.rb -- --with-verbose
```

You can also add the extra option via rake-compiler gem.

```
$ rake compiler -- --with-verbose
```

If the extra option is not given, the value of the
`RbConfig::CONFIG["MKMF_VERBOSE"]` enabled by the configure option below is
used.

```
$ ./configure --enable-mkmf-verbose
```

For the unit tests, updated the following files.

* The `test/mkmf/test_configuration.rb` was created to test the cases with the
  `configuration` method and this implementation.
* Updated the `TestMkmf#assert_separately` to set the extra
  arguments in `test/mkmf/base.rb`. Updated tests using the `assert_separately`.
* Added tests for `MakeMakefile#with_config` in the `test/mkmf/test_config.rb`.

[1] https://www.gnu.org/software/make/manual/html_node/Variables_002fRecursion.html

Fixes [Bug #19695]

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/test/mkmf/base.rb b/test/mkmf/base.rb
index ec42bca100..7df07c16a6 100644
--- a/test/mkmf/base.rb
+++ b/test/mkmf/base.rb
@@ -147,7 +147,10 @@ class TestMkmf < Test::Unit::TestCase
 
   include Base
 
-  def assert_separately(args, src, *rest, **options)
-    super(args + ["-r#{__FILE__}"], "extend TestMkmf::Base; setup\nEND{teardown}\n#{src}", *rest, **options)
+  def assert_separately(args, extra_args, src, *rest, **options)
+    super(args + ["-r#{__FILE__}"] + %w[- --] + extra_args,
+          "extend TestMkmf::Base; setup\nEND{teardown}\n#{src}",
+          *rest,
+          **options)
   end
 end