For mruby gem mruby-compiler, needed by mruby-eval.
mrbgems/mruby-compiler/core/parse.y: In function 'parser_yylex':
mrbgems/mruby-compiler/core/parse.y:5785:23: error: implicit declaration of function 'tolower' [-Werror=implicit-function-declaration]
5785 | tokadd(p, tolower(c));
| ^~~~~~~
For mruby gem
mruby-compiler
, needed bymruby-eval
.