Trying to install Ruby gems on Synology DiskStation DS216j, cannot find Ruby header files -

i trying run ruby scripts on synology diskstation ds216j. managed install ruby 2.3.1 via opkg/entware-ng when try install gems native extensions, error:

$ sudo gem install io-console  building native extensions.  take while... error:  error installing io-console:     error: failed build gem native extension.      current directory: /volume1/@entware-ng/opt/lib/ruby/gems/2.3/gems/io-console-0.4.6 /opt/bin/ruby -r ./siteconf20161113-31591-ucvjgl.rb extconf.rb *** extconf.rb failed *** not create makefile due reason, lack of necessary libraries and/or headers.  check mkmf.log file more details.  may need configuration options.  provided configuration options:     --with-opt-dir     --without-opt-dir     --with-opt-include     --without-opt-include=${opt-dir}/include     --with-opt-lib     --without-opt-lib=${opt-dir}/lib     --with-make-prog     --without-make-prog     --srcdir=.     --curdir     --ruby=/opt/bin/$(ruby_base_name) /opt/lib/ruby/2.3/mkmf.rb:456:in `try_do': compiler failed generate executable file. (runtimeerror) have install development tools first.     /opt/lib/ruby/2.3/mkmf.rb:571:in `block in try_compile'     /opt/lib/ruby/2.3/mkmf.rb:524:in `with_werror'     /opt/lib/ruby/2.3/mkmf.rb:571:in `try_compile'     /opt/lib/ruby/2.3/mkmf.rb:835:in `macro_defined?'     extconf.rb:7:in `<main>'  see why extension failed compile, please check mkmf.log can found here:    /opt/lib/ruby/gems/2.3/extensions/arm-linux/2.3/io-console-0.4.6/mkmf.log  extconf failed, exit code 1  gem files remain installed in /opt/lib/ruby/gems/2.3/gems/io-console-0.4.6 inspection. results logged /opt/lib/ruby/gems/2.3/extensions/arm-linux/2.3/io-console-0.4.6/gem_make.out 

the content of /opt/lib/ruby/gems/2.3/extensions/arm-linux/2.3/io-console-0.4.6/mkmf.log:

"arm-openwrt-linux-gnueabi-gcc -o conftest -i/opt/include/ruby-2.3/arm-linux-gnu -i/opt/include/ruby-2.3/ruby/backward -i/opt/include/ruby-2.3 -i. -i/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/include -i/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/include -i/media/ware3/entware-ng.2016.08/staging_dir/toolchain-arm_cortex-a9_gcc-5.4.0_glibc-2.23_eabi/usr/include -i/media/ware3/entware-ng.2016.08/staging_dir/toolchain-arm_cortex-a9_gcc-5.4.0_glibc-2.23_eabi/include -i/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libiconv-full/include -i/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libintl-full/include  -d_file_offset_bits=64  -o2 -pipe -march=armv7-a -mtune=cortex-a9 -fno-caller-saves -fhonour-copts -wno-error=unused-but-set-variable -wno-error=unused-result -mfloat-abi=soft  -i/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libiconv-full/include -i/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libintl-full/include  -fpic conftest.c  -l. -l/opt/lib -l. -l/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib -l/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/lib -wl,-rpath,/opt/lib -wl,-rpath-link=/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib -wl,--dynamic-linker=/opt/lib/ld-linux.so.3 -l/media/ware3/entware-ng.2016.08/staging_dir/toolchain-arm_cortex-a9_gcc-5.4.0_glibc-2.23_eabi/usr/lib -l/media/ware3/entware-ng.2016.08/staging_dir/toolchain-arm_cortex-a9_gcc-5.4.0_glibc-2.23_eabi/lib -l/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libiconv-full/lib -wl,-rpath-link=/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libiconv-full/lib -l/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libintl-full/lib -wl,-rpath-link=/media/ware3/entware-ng.2016.08/staging_dir/target-arm_cortex-a9_glibc-2.23_eabi/opt/lib/libintl-full/lib -l/media/ware3/entware-ng.2016.08/build_dir/target-arm_cortex-a9_glibc-2.23_eabi/ruby-2.3.1  -fstack-protector -rdynamic -wl,-export-dynamic     -lruby  -lpthread -lgmp -ldl -lcrypt -lm   -lc" /opt/bin/ld: cannot find -lruby collect2: error: ld returned 1 exit status checked program was: /* begin */ 1: #include "ruby.h" 2:  3: int main(int argc, char **argv) 4: { 5:   return 0; 6: } /* end */ 

/opt/bin/ld: cannot find -lruby seems real error here.

googling results in recommendations install ruby source code/headers which did:

$ wget -qo- http://pkg.entware.net/binaries/armv7/include/include.tar.gz | tar xvz -c /opt/include  [snip]  $ ls -lah /opt/include/ruby-2.3/  drwxr-xr-x    4 1000     1000        4.0k aug 19 12:42 . drwxr-xr-x  179 root     root       20.0k oct 10 09:32 .. drwxr-xr-x    3 1000     1000        4.0k aug 19 12:42 arm-linux-gnu drwxr-xr-x    3 1000     1000        4.0k aug 19 12:42 ruby -rw-r--r--    1 1000     1000         868 jul 11  2012 ruby.h 

so guess real question is: how can tell /opt/bin/ld ruby header files located in /opt/include/ruby-2.3/?

any or tips appreciated, thanks!

/opt/bin/ld: cannot find -lruby means linker can't find ruby library, not headers. need compiled shared object library @ /opt/lib/libruby.so or static library /opt/lib/libruby-static.a.