[Integration] Fix issue when a build configuration contains a slash

Fixes #2767

CHANGELOG.md

@@ -17,6 +17,11 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Kyle Fuller](https://github.com/kylef)
   [#2803](https://github.com/CocoaPods/CocoaPods/issues/2803)
 
+* Fixes an issue with integrating into projects where there is a slash in the
+  build configuration name.  
+  [Kyle Fuller](https://github.com/kylef)
+  [#2767](https://github.com/CocoaPods/CocoaPods/issues/2767)
+
 * Pods will use `CLANG_ENABLE_OBJC_ARC = 'YES'` instead of
   `CLANG_ENABLE_OBJC_ARC = 'NO'`. For pods with `requires_arc = false` the
   `-fno-objc-arc` flag will be specified for the all source files.  

lib/cocoapods/target.rb

@@ -83,7 +83,7 @@ module Pod
     #
     def xcconfig_path(variant = nil)
       if variant
-        support_files_dir + "#{label}.#{variant.downcase}.xcconfig"
+        support_files_dir + "#{label}.#{variant.gsub(File::SEPARATOR, '-').downcase}.xcconfig"
       else
         support_files_dir + "#{label}.xcconfig"
       end

spec/unit/target/pod_target_spec.rb

@@ -68,6 +68,12 @@ module Pod
         )
       end
 
+      it 'escapes the file separators in variant build configuration name in the xcconfig file' do
+        @pod_target.xcconfig_path("Release#{File::SEPARATOR}1").to_s.should.include?(
+          'Pods/Target Support Files/Pods-BananaLib/Pods-BananaLib.release-1.xcconfig'
+        )
+      end
+
       it 'returns the absolute path of the target header file' do
         @pod_target.target_environment_header_path.to_s.should.include?(
           'Pods/Target Support Files/Pods/Pods-environment.h'