Bump sassc and fix LoadErrors

There seems to be a portability issue in the sassc gem that attempts to execute illegal instruction which subsequently manifest themselves as Ruby LoadErrors. The workaround for this problem is to uninstall the gem (if already installed) and then reinstall it without tuning the native extension code for the CPU architecture. This leads to marginally less efficient code, however this is acceptable since libsass is only used when precompiling assets.

More information is available at the following GitHub issue page for the sassc gem:
sass/sassc-ruby#146

Gemfile

@@ -5,8 +5,12 @@ ruby '2.6.3'
 # Application config
 gem 'dotenv-rails', '~> 2.7', require: 'dotenv/rails-now'
 
-# Pin version of sassc because there seems to be a bug on macOS
-gem 'sassc', '= 2.0.1'
+# A portability issue in the sassc gem exists on several platforms.
+# If this causes you issues (LoadErrors) then run the following commands:
+#   1) gem uninstall sassc
+#   2) gem install sassc -- --disable-march-tune-native
+#   3) bundle install
+gem 'sassc', '~> 2.2'
 
 # Rails
 gem 'rails', '~> 6.0.0'

Gemfile.lock

@@ -391,9 +391,8 @@ GEM
     rubyzip (2.0.0)
     sass-rails (6.0.0)
       sassc-rails (~> 2.1, >= 2.1.1)
-    sassc (2.0.1)
+    sassc (2.2.1)
       ffi (~> 1.9)
-      rake
     sassc-rails (2.1.2)
       railties (>= 4.0.0)
       sassc (>= 2.0)
@@ -540,7 +539,7 @@ DEPENDENCIES
   rotp (~> 5.1)
   rqrcode (~> 1.1.1)
   sass-rails (~> 6.0)
-  sassc (= 2.0.1)
+  sassc (~> 2.2)
   secure_headers (~> 6.1)
   selenium-webdriver (~> 3.142)
   sentry-raven (~> 2.11)