If $rake_root_fiber is used, sh runs command in another Fiber. If
command is ran in another Fiber, "rescue RuntimEerror" can't rescue
exception for system(...) failure.
How to reproduce:
$ CC="gcc -std=gnu99" ./minirake
(in /home/kou/work/ruby/mruby.kou)
CC mrbgems/mruby-compiler/core/codegen.c -> build/test/mrbgems/mruby-compiler/core/codegen.o
sh: 1: gcc -std=gnu99: not found
rake aborted!
Command Failed: ["gcc -std=gnu99" -g -std=gnu99 ...]
mimaki