brace the fact that lchmod(2) can EOPNOTSUPP

Musl libc has this function as a tiny wrapper of fchmodat(3posix).  On
the other hand Linux kernel does not support changing modes of a symlink.
The operation always fails with EOPNOTSUPP.  This fchmodat behaviour is
defined in POSIX.  We have to take care of such exceptions.

lib/fileutils.rb

@@ -1345,6 +1345,7 @@ module FileUtils
       else
         File.chmod mode, path()
       end
+    rescue Errno::EOPNOTSUPP
     end
 
     def chown(uid, gid)
@@ -1439,7 +1440,7 @@ module FileUtils
       if st.symlink?
         begin
           File.lchmod mode, path
-        rescue NotImplementedError
+        rescue NotImplementedError, Errno::EOPNOTSUPP
         end
       else
         File.chmod mode, path

test/pathname/test_pathname.rb

@@ -818,7 +818,7 @@ class TestPathname < Test::Unit::TestCase
       old = path.lstat.mode
       begin
         path.lchmod(0444)
-      rescue NotImplementedError
+      rescue NotImplementedError, Errno::EOPNOTSUPP
         next
       end
       assert_equal(0444, path.lstat.mode & 0777)

test/ruby/test_notimp.rb

@@ -13,11 +13,11 @@ class TestNotImplement < Test::Unit::TestCase
 
   def test_respond_to_lchmod
     assert_include(File.methods, :lchmod)
-    if /linux/ =~ RUBY_PLATFORM
-      assert_equal(false, File.respond_to?(:lchmod))
-    end
-    if /freebsd/ =~ RUBY_PLATFORM
+    case RUBY_PLATFORM
+    when /freebsd/, /linux-musl/
       assert_equal(true, File.respond_to?(:lchmod))
+    when /linux/
+      assert_equal(false, File.respond_to?(:lchmod))
     end
   end
 
@@ -57,9 +57,14 @@ class TestNotImplement < Test::Unit::TestCase
         File.open(f, "w") {}
         File.symlink f, g
         newmode = 0444
-        File.lchmod newmode, "#{d}/g"
-        snew = File.lstat(g)
-        assert_equal(newmode, snew.mode & 0777)
+        begin
+          File.lchmod newmode, "#{d}/g"
+        rescue Errno::EOPNOTSUPP
+          skip $!
+        else
+          snew = File.lstat(g)
+          assert_equal(newmode, snew.mode & 0777)
+        end
       }
     end
   end