Without the change parallel installs fail as:
installing rdoc: ...-ruby-2.7.7-devdoc/share/ri/2.7.0/system
Traceback (most recent call last):
13: from ./tool/rbinstall.rb:954:in `<main>'
12: from ./tool/rbinstall.rb:954:in `each'
11: from ./tool/rbinstall.rb:957:in `block in <main>'
10: from ./tool/rbinstall.rb:438:in `block in <main>'
9: from ./tool/rbinstall.rb:262:in `install_recursive'
8: from ./tool/rbinstall.rb:262:in `each'
7: from ./tool/rbinstall.rb:271:in `block in install_recursive'
6: from ./tool/rbinstall.rb:174:in `install'
5: from /build/ruby-2.7.7/lib/fileutils.rb:876:in `install'
4: from /build/ruby-2.7.7/lib/fileutils.rb:1587:in `fu_each_src_dest'
3: from /build/ruby-2.7.7/lib/fileutils.rb:1605:in `fu_each_src_dest0'
2: from /build/ruby-2.7.7/lib/fileutils.rb:1589:in `block in fu_each_src_dest'
1: from /build/ruby-2.7.7/lib/fileutils.rb:882:in `block in install'
/build/ruby-2.7.7/lib/fileutils.rb:882:in `chmod': No such file or directory @ apply2files - ...-ruby-2.7.7-devdoc/share/ri/2.7.0/system/ARGF/inspect-i.ri (Errno::ENOENT)
make: *** [uncommon.mk:373: do-install-all] Error 1
make: *** Waiting for unfinished jobs....
Sergei Trofimovich
8dd301559a