Fix source validation for local URLs and SSH repos

Fix `INFOPLIST_FILE` being overridden when set in `pod_target_xcconfig`

Release 1.5.3

# gpg: Signature made Thu May 24 22:49:47 2018 PDT
# gpg:                using RSA key 01195BB315DDA856
# gpg: Good signature from "Samuel Giddins <segiddins@segiddins.me>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 7B19 37A9 CF66 AEF6 52C9  4090 0119 5BB3 15DD A856

# Conflicts:
#	Gemfile.lock
#	lib/cocoapods/generator/xcconfig/aggregate_xcconfig.rb
#	spec/cocoapods-integration-specs
#	spec/unit/installer/xcode/pods_project_generator_spec.rb

Raise an error if user target `SWIFT_VERSION` is missing

Be defensive when passing potentially nil strings to Gem::Version

(cherry picked from commit 04cbea4d)

Fix compatibility with RubyGems v2.7.7

Done by using Pod::Version instead of Gem::Version, which in 2.7.7 stop allowing initializing a version with `nil`

Remove analyzer `attr_accessor` properties

Do not symlink headers that belong to test specs

Be defensive when passing potentially nil strings to Gem::Version

Fix a bug that umbrella  header import fails in a specific case

Attempt to parse `SWIFT_VERSION` from xcconfig during target inspection

Do not try to integrate uncreated test native targets

Warn if 'git://' protocol is used as the source of a pod

Split test resource bundles installed by each test spec

Do not build pod target if it contains script phases

Do not overwrite App host info plist path for multiple test specs

Link vendored static libraries into dynamic frameworks

This fixes missing symbol errors at link time

This mirrors the treatment vendored static libraries get

Allow EXPANDED_CODE_SIGN_IDENTITY to be unset

This is unset for some test target configurations.

Stop linking frameworks to static libraries to avoid warnings with th…