CI doesn't support clang-format, don't fail the test gen script if it…

… is missing

data_lang/utf8_decoder_tests_gen.sh

@@ -2,4 +2,9 @@
 
 mkdir -p _gen/test/utf8
 python3 data_lang/utf8_decoder_tests_gen.py >_gen/test/utf8/decoder-exhaustive.inc
-clang-format -i _gen/test/utf8/decoder-exhaustive.inc
+
+# Try to format, but clang-format isn't always available (eg. CI)
+if ! clang-format -i _gen/test/utf8/decoder-exhaustive.inc; then
+  echo 'Failed to run clang-format on generated decoder tests.'
+  echo 'Make sure it is installed if you want _gen/test/utf8/decoder-exhaustive.inc to be human readable.'
+fi