Add compatibility for Xcode 12

[godrei]

Hi @vfxdrummer , thanks for the contribution.

The changes fails at bundle install:

+------------------------------------------------------------------------------+
| (0) bundle install                                                           |
+------------------------------------------------------------------------------+
| id: script                                                                   |
| version: 1.1.6                                                               |
| collection: https://github.com/bitrise-io/bitrise-steplib.git                |
| toolkit: bash                                                                |
| time: 2020-10-15T09:06:00Z                                                   |
+------------------------------------------------------------------------------+
|                                                                              |
Fetching gem metadata from https://rubygems.org/........
Fetching CFPropertyList 3.0.1
Installing CFPropertyList 3.0.1
Using public_suffix 2.0.5
Fetching addressable 2.7.0
Installing addressable 2.7.0
Fetching ast 2.4.0
Installing ast 2.4.0
Using atomos 0.1.3
Fetching babosa 1.0.3
Installing babosa 1.0.3
Using bundler 1.17.3
Fetching claide 1.0.3
Installing claide 1.0.3
Using colored 1.2
Using colored2 3.1.2
Using highline 1.7.10
Using commander-fastlane 4.4.6
Using declarative 0.0.10
Using declarative-option 0.1.0
Fetching diff-lcs 1.3
Installing diff-lcs 1.3
Using digest-crc 0.4.1
Using unf_ext 0.0.7.6
Using unf 0.1.4
Using domain_name 0.5.20190701
Fetching dotenv 2.7.5
Installing dotenv 2.7.5
Using emoji_regex 1.0.1
Fetching excon 0.67.0
Installing excon 0.67.0
Using multipart-post 2.0.0
Using faraday 0.15.4
Using http-cookie 1.0.3
Using faraday-cookie_jar 0.0.6
Using faraday_middleware 0.13.1
Fetching fastimage 2.1.7
Installing fastimage 2.1.7
Using gh_inspector 1.1.3
Using jwt 2.1.0
Using memoist 0.16.0
Using multi_json 1.13.1
Using os 1.0.1
Using signet 0.11.0
Using googleauth 0.6.7
Using httpclient 2.8.3
Fetching mime-types-data 3.2019.0904
Installing mime-types-data 3.2019.0904
Fetching mime-types 3.3
Installing mime-types 3.3
Using uber 0.1.0
Using representable 3.0.4
Using retriable 3.1.2
Using google-api-client 0.23.9
Fetching google-cloud-env 1.2.1
Installing google-cloud-env 1.2.1
Fetching google-cloud-core 1.3.1
Installing google-cloud-core 1.3.1
Using google-cloud-storage 1.16.0
Fetching json 2.2.0
Installing json 2.2.0 with native extensions
Using mini_magick 4.9.5
Using multi_xml 0.6.0
Fetching plist 3.5.0
Installing plist 3.5.0
Using rubyzip 1.3.0
Using security 0.1.3
Using naturally 2.2.0
Fetching simctl 1.6.6
Installing simctl 1.6.6
Using slack-notifier 2.3.2
Using terminal-notifier 2.0.0
Fetching unicode-display_width 1.6.0
Installing unicode-display_width 1.6.0
Fetching terminal-table 1.8.0
Installing terminal-table 1.8.0
Using tty-screen 0.7.0
Using tty-cursor 0.7.0
Using tty-spinner 0.9.1
Using word_wrap 1.0.0
Using nanaimo 0.2.6
Fetching xcodeproj 1.18.0
Downloading xcodeproj-1.18.0 revealed dependencies not in the API or the
lockfile (nanaimo (~> 0.3.0)).
Either installing with `--full-index` or running `bundle update xcodeproj`
should fix the problem.
|                                                                              |
+---+---------------------------------------------------------------+----------+
| x | bundle install (exit code: 34)                                | 20.69 sec|
+---+---------------------------------------------------------------+----------+
| Issue tracker: https://github.com/bitrise-io/steps-script/issues             |
| Source: https://github.com/bitrise-io/steps-script                           |
+---+---------------------------------------------------------------+----------+

there is another PR for updating gems, I am going to close this one and merge the other one to speed up the gem update.