https://git.ruby-lang.org/ruby.git/commit/?id=ca85f16a7d

From ca85f16a7dc50145a61998c5caed2d49ef48b73c Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@r...>
Date: Fri, 25 Mar 2022 17:33:30 +0900
Subject: ext/psych/extconf.rb: Fail when libyaml is unavailable

WHen libyaml is not installed, make fails with the following cryptic
message:

```
gmake[2]: Entering directory '/home/chkbuild/chkbuild-crossruby/tmp/build/20220325T045825Z/ruby/ext/psych'
gmake[2]: *** No rule to make target 'yaml/yaml.h', needed by 'psych.o'.  Stop.
gmake[2]: Leaving directory '/home/chkbuild/chkbuild-crossruby/tmp/build/20220325T045825Z/ruby/ext/psych'
```

I think it should give up building psych with a clear message.
---
 ext/psych/extconf.rb | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/ext/psych/extconf.rb b/ext/psych/extconf.rb
index 7da73760e3..0e4fb86a0b 100644
--- a/ext/psych/extconf.rb
+++ b/ext/psych/extconf.rb
@@ -10,6 +10,11 @@ dir_config 'libyaml' https://github.com/ruby/ruby/blob/trunk/ext/psych/extconf.rb#L10
 if enable_config("bundled-libyaml", false) || !pkg_config('yaml-0.1') && !(find_header('yaml.h') && find_library('yaml', 'yaml_get_version'))
   # Embed libyaml since we could not find it.
 
+  unless File.exist?("#{$srcdir}/yaml")
+    puts "failed to build psych because no libyaml is available"
+    exit
+  end
+
   $VPATH << "$(srcdir)/yaml"
   $INCFLAGS << " -I$(srcdir)/yaml"
 
-- 
cgit v1.2.1


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