Failed to install due to permission error

[GuerrillaCoder]

I am trying to install this gem on ruby2.3 running on windows 10 ubuntu 14.04.

This is the error output from console:

root@localhost:~/wpscan# gem install yajl-ruby
Building native extensions.  This could take a while...
ERROR:  Error installing yajl-ruby:
        ERROR: Failed to build gem native extension.

    current directory: /var/lib/gems/2.3.0/gems/yajl-ruby-1.2.1/ext/yajl
/usr/bin/ruby2.3 -r ./siteconf20160418-17885-1ozd9d8.rb extconf.rb
creating Makefile

current directory: /var/lib/gems/2.3.0/gems/yajl-ruby-1.2.1/ext/yajl
make "DESTDIR=" clean

current directory: /var/lib/gems/2.3.0/gems/yajl-ruby-1.2.1/ext/yajl
make "DESTDIR="
compiling yajl.c
compiling yajl_alloc.c
compiling yajl_buf.c
compiling yajl_encode.c
compiling yajl_ext.c
yajl_ext.c: In function ‘rb_yajl_parser_parse’:
yajl_ext.c:471:17: warning: variable ‘stat’ set but not used [-Wunused-but-set-variable]
     yajl_status stat;
                 ^
compiling yajl_gen.c
compiling yajl_lex.c
compiling yajl_parser.c
compiling yajl_version.c
linking shared-object yajl/yajl.so

current directory: /var/lib/gems/2.3.0/gems/yajl-ruby-1.2.1/ext/yajl
make "DESTDIR=" install
/usr/bin/install -c -m 0755 yajl.so ./.gem.20160418-17885-1ldn81y/yajl

Permission denied @ rb_file_s_rename - (./.gem.20160418-17885-1ldn81y/yajl, /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/yajl-ruby-1.2.1/yajl)

Gem files will remain installed in /var/lib/gems/2.3.0/gems/yajl-ruby-1.2.1 for inspection.
Results logged to /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/yajl-ruby-1.2.1/gem_make.out
root@localhost:~/wpscan#

I am running as root, not sure why I am getting permission denied.

Anyone have any ideas?

[GuerrillaCoder]

I manually created the directory and it worked