mruby: fix build (#7759)
mruby: fix build (#7759)

* mruby: fix build

Ref: https://github.com/google/oss-fuzz/issues/7736

* nit
skia-dev/oss-fuzz,robertswiecki/oss-fuzz,skia-dev/oss-fuzz,skia-dev/oss-fuzz,skia-dev/oss-fuzz,skia-dev/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,robertswiecki/oss-fuzz,skia-dev/oss-fuzz,robertswiecki/oss-fuzz,skia-dev/oss-fuzz,google/oss-fuzz,skia-dev/oss-fuzz,robertswiecki/oss-fuzz,robertswiecki/oss-fuzz,skia-dev/oss-fuzz,robertswiecki/oss-fuzz,google/oss-fuzz,robertswiecki/oss-fuzz,robertswiecki/oss-fuzz,google/oss-fuzz,robertswiecki/oss-fuzz,google/oss-fuzz,skia-dev/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,skia-dev/oss-fuzz,robertswiecki/oss-fuzz,robertswiecki/oss-fuzz,google/oss-fuzz