Resolve abi symbol references from miniruby to avoid circular deps

Adding `ruby` to `PREP` causes the following circular dependencies
because `PREP` is used as a prerequisite by some targets required to
build `ruby` target itself.
```
make: Circular .rbconfig.time <- ruby dependency dropped.
make: Circular builtin_binary.inc <- ruby dependency dropped.
make: Circular ext/extinit.c <- ruby dependency dropped.
make: Circular ruby <- ruby dependency dropped.
```

Adding a new Make variable like `EXTPREP` only for exts may be also
reasonable, but it would introduce another complexity into our build
system. `-bundle_loader` doesn't care that link-time and run-time
loader executables are different as long as bound symbols are provided,
so it's ok to resolve from miniruby to simplify our build.

1 files changed, 1 insertions, 1 deletions

diff --git a/ext/extmk.rb b/ext/extmk.rb
index b0d84ef00f..1624ec9099 100755
--- a/ext/extmk.rb
+++ b/ext/extmk.rb
@@ -427,7 +427,7 @@ end
 topruby = $ruby
 $ruby = topruby.join(' ')
 $mflags << "ruby=#$ruby"
-$builtruby = '$(topdir)/ruby' + EXEEXT # Must be an executable path
+$builtruby = '$(topdir)/miniruby' + EXEEXT # Must be an executable path
 
 MTIMES = [__FILE__, 'rbconfig.rb', srcdir+'/lib/mkmf.rb'].collect {|f| File.mtime(f)}