[PATCH] Fix issue #4841: do not use internal ruby include paths

Building subversion with ruby2.7 produces a compilation warning:

subversion/bindings/swig/ruby/svn_client.c:1666:13: warning: implicit declaration of function ‘assert’ [-Wimplicit-function-declaration]
 1666 | assert(own); /* badly formed typemap which will lead to a memory leak - it must set and use own to delete *ptr */
 | ^~~~~~

And later tests fail with:

/usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require': /build/subversion/src/subversion-1.13.0/subversion/bindings/swig/ruby/libsvn_swig_ruby/.libs/libsvn_swig_ruby-1.so.0: undefined symbol: assert - /build/subversion/src/subversion-1.13.0/subversion/bindings/swig/ruby/.ext/svn/ext/core.so (LoadError)
        from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require'
        from /build/subversion/src/subversion-1.13.0/subversion/bindings/swig/ruby/svn/error.rb:21:in `<top (required)>'
        from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require'
        from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require'
        from /build/subversion/src/subversion-1.13.0/subversion/bindings/swig/ruby/svn/core.rb:25:in `<top (required)>'
        from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require'
        from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require'
        from /build/subversion/src/subversion-1.13.0/subversion/bindings/swig/ruby/test/run-test.rb:47:in `<main>'
make: *** [Makefile:962: check-swig-rb] Error 1

It turns out that ruby 2.7 added a new header file '$RUBY_TOP/ruby/assert.h'.
Subversion includes both $RUBY_TOP and $RUBY_TOP/ruby and it makes "assert.h" to
be resolved to ruby's version instead of libc one.

To fix this problem subversion should use only $RUBY_TOP and avoid using internal ruby paths.

 * build/ac-macros/swig.m4: cleanup ruby include path

---
 build/ac-macros/swig.m4 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/build/ac-macros/swig.m4 b/build/ac-macros/swig.m4
index bc2599038f..c707a8c282 100644
--- a/build/ac-macros/swig.m4
+++ b/build/ac-macros/swig.m4
@@ -230,7 +230,7 @@ AC_DEFUN(SVN_FIND_SWIG,
     AC_CACHE_CHECK([for Ruby include path], [svn_cv_ruby_includes],[
     if test -d "$rbconfig_rubyhdrdir"; then
       dnl Ruby >=1.9
-      svn_cv_ruby_includes="-I. -I$rbconfig_rubyhdrdir -I$rbconfig_rubyhdrdir/ruby -I$rbconfig_rubyhdrdir/ruby/backward"
+      svn_cv_ruby_includes="-I. -I$rbconfig_rubyhdrdir"
       if test -d "$rbconfig_rubyarchhdrdir"; then
         dnl Ruby >=2.0
         svn_cv_ruby_includes="$svn_cv_ruby_includes -I$rbconfig_rubyarchhdrdir"
-- 
2.24.1