Fix library name for onigmo

[ksss]

Onigmo library name is onigmo ref https://github.com/k-takata/Onigmo/blob/27fa4fbbcb064c5e18870081fbd652461db34239/README.md#usage

[mattn]

On Linux, libonig.so.4 is provided.

$ dpkg -L libonig4 | grep onig
/lib/x86_64-linux-gnu/libonig.so.4.0.0
/share/doc/libonig4
/share/doc/libonig4/changelog.Debian.gz
/share/doc/libonig4/copyright
/lib/x86_64-linux-gnu/libonig.so.4

[ksss]

Islibonig oniguruma? Could you compile with #include <onigmo.h>?

# apt-get install libonig-dev
...
# dpkg -L libonig5 | grep onig
/usr/lib/x86_64-linux-gnu/libonig.so.5.0.0
/usr/share/doc/libonig5
/usr/share/doc/libonig5/changelog.Debian.gz
/usr/share/doc/libonig5/copyright
/usr/lib/x86_64-linux-gnu/libonig.so.5

cat /usr/share/doc/libonig5/copyright | grep Source
Source: https://github.com/kkos/oniguruma

# cat onigmo.c
#include <onigmo.h>
int main(int argc, const char *argv) {
  return 0;
}

# gcc onigmo.c
t.c:1:10: fatal error: onigmo.h: No such file or directory
 #include <onigmo.h>
          ^~~~~~~~~~
compilation terminated.

[mattn]

Ah, you are right.