Backport upstream pull request for ruby3.2 build issue

Add -Werror=implicit-function explicitly to detect such function

ruby-shadow-2.5.1-extconf-ruby32-fix.patch

@@ -0,0 +1,29 @@
+commit eab4aba3f5e06ea8f124d3e5ff6b3fa88c4807cd
+Author: Mamoru TASAKA <mtasaka@fedoraproject.org>
+Date:   Thu Dec 1 12:23:05 2022 +0900
+
+    extconf.rb: use Rbconfig::CONFIG instead of mkmf CONFIG
+    
+    In mkmf.rb CONFIG is defined as CONFIG is defined as RbConfig::MAKEFILE_CONFIG
+    and RbConfig::MAKEFILE_CONFIG is almost same as RbConfig::CONFIG
+    except that RbConfig::MAKEFILE_CONFIG uses reference for other variables.
+    
+    Using CONFIG in extconf.rb causes error with ruby3.2 because now
+    CONFIG['host_os'] uses reference for target_os variable, and extconf.rb
+    expects that this variable is all expanded. So instead, use RbConfig::CONFIG .
+    
+    Closes #30
+
+diff --git a/extconf.rb b/extconf.rb
+index d17f926..55dcff5 100644
+--- a/extconf.rb
++++ b/extconf.rb
+@@ -14,7 +14,7 @@ $CFLAGS = case RUBY_VERSION
+           else; ''
+           end
+ 
+-implementation = case CONFIG['host_os']
++implementation = case RbConfig::CONFIG['host_os']
+                  when /linux/i; 'shadow'
+                  when /sunos|solaris/i; 'shadow'
+                  when /freebsd|mirbsd|netbsd|openbsd/i; 'pwd'