support cocoapods-binary

[shtnkgm]

When use leavez/cocoapods-binary, source code of libraries is placed under Pods/_Prebuild directory.
Therefore, the license information is not created correctly.

To download source code, I wrote keep_source_code_for_prebuilt_frameworks! option in Podfile.

plugin 'cocoapods-binary'

platform :ios, '13.0'
use_frameworks!
keep_source_code_for_prebuilt_frameworks!
all_binary!

target 'MyApp' do
    pod 'SomeLibrary'
end