ruby/ruby — pull request #571 by knu (2014-03-20 15:15:57+00:00)
Title: Fix a build problem with clang and --with-opt-dir.

* configure.in: Fix a build problem with clang and --with-opt-dir.
If ruby is configured with --with-opt-dir=dir when using clang
as compiler, a warning `clang: warning: argument unused during
compilation: '-I dir'` is emitted almost every time clang
compiles a file. Unfortunately, RUBY_CHECK_PRINTF_PREFIX takes
any output from the compiler as fatal error, and the check thus
fails due to the warning. This is an attempt to fix the problem
by adding a flag -Qunused-arguments to CFLAGS locally in the
function to suppress the warning.