Failure to install old mysql2 gem - ruby-on-rails

Question

I am using Mac High Sierra. I am using Ruby 2.2.1 with RVM. I need to use mysql2 with this Ruby on Rails app. I do have mysql 5.7 installed. I do have xcode installed along with the command-line tools.
I am simply trying to get this company app working on my local machine. I know that I am very close but I have one final error when I do bundle install I receive the following error when I get to the mysql2 gem:
Fetching mysql2 0.3.18
Installing mysql2 0.3.18 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
current directory: /Users/ahayden/.rvm/gems/ruby-2.2.1/gems/mysql2-0.3.18/ext/mysql2
/Users/ahayden/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20180710-52515-2hjll8.rb extconf.rb
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for rb_thread_blocking_region()... no
checking for rb_wait_for_single_fd()... yes
checking for rb_hash_dup()... yes
checking for rb_intern3()... yes
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Using mysql_config at /usr/local/bin/mysql_config
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checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
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Don't know how to set rpath on your system, if MySQL libraries are not in path mysql2 may not load
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Setting libpath to /usr/local/Cellar/mysql-connector-c/6.1.11/lib
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creating Makefile
current directory: /Users/ahayden/.rvm/gems/ruby-2.2.1/gems/mysql2-0.3.18/ext/mysql2
make "DESTDIR=" clean
current directory: /Users/ahayden/.rvm/gems/ruby-2.2.1/gems/mysql2-0.3.18/ext/mysql2
make "DESTDIR="
compiling infile.c
compiling client.c
client.c:359:33: warning: implicit conversion loses integer precision: 'long' to 'unsigned int' [-Wshorten-64-to-32]
elapsed_time = end_time - start_time;
~ ~~~~~~~~~^~~~~~~~~~~~
client.c:1163:56: warning: implicit conversion loses integer precision: 'size_t' (aka 'unsigned long') to 'unsigned int' [-Wshorten-64-to-32]
mysql2rb = mysql2_mysql_enc_name_to_rb(charset_name, charset_name_len);
~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~
2 warnings generated.
compiling mysql2_ext.c
compiling result.c
result.c:186:17: warning: comparison of integers of different signs: 'int' and 'unsigned long' [-Wsign-compare]
for (i = 0; i < (len - 1); i++) {
~ ^ ~~~~~~~
1 warning generated.
linking shared-object mysql2/mysql2.bundle
ld: library not found for -l-lpthread
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [mysql2.bundle] Error 1
make failed, exit code 2
Gem files will remain installed in /Users/ahayden/.rvm/gems/ruby-2.2.1/gems/mysql2-0.3.18 for inspection.
Results logged to /Users/ahayden/.rvm/gems/ruby-2.2.1/extensions/x86_64-darwin-17/2.2.0/mysql2-0.3.18/gem_make.out
An error occurred while installing mysql2 (0.3.18), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.18'` succeeds before bundling.
In Gemfile:
mysql2
I've tried just installing mysql2 without the specific gem version and it works, but it did not fix my problem. It seems to boil down to the bottom of the traceback where it cannot find library -l-lpthread. Please help, I've been trying to do this all day.

Answer 1

This fixed it for me
gem install mysql2 -v '0.3.21' -- --with-cflags=\"-I/usr/local/opt/openssl/include\" --with-ldflags=\"-L/usr/local/opt/openssl/lib\"
after installing openssl
brew install openssl

Answer 2

As per the description shared it seems like the mysql dependencies are unable to install.
First we need to ‘locate mysql_config’ and then replace the path in the following command with where that file is.
gem install mysql2 -- --with-mysql-config=/usr/local/mysql/bin/mysql_config