Make symlinking headers work with specs which overwrite Spec#copy_header_mapping.

lib/cocoapods/installer.rb

@@ -30,6 +30,7 @@ module Pod
         @xcconfig ||= Xcodeproj::Config.new({
           # In a workspace this is where the static library headers should be found.
           'HEADER_SEARCH_PATHS' => '"Pods/Headers"',
+          'ALWAYS_SEARCH_USER_PATHS' => 'YES',
           # This makes categories from static libraries work, which many libraries
           # require, so we add these by default.
           'OTHER_LDFLAGS'            => '-ObjC -all_load',
@@ -98,9 +99,11 @@ module Pod
           spec.copy_header_mappings.each do |header_dir, files|
             target_dir = "#{headers_symlink_path_name}/#{header_dir}"
             FileUtils.mkdir_p(target_dir)
-            Dir.chdir(target_dir) do
-              files.each do |file|
-                FileUtils.ln_s("../../#{file}", file.basename)
+            target_dir_real_path = Pathname.new(target_dir).realpath
+            files.each do |file|
+              source = Pathname.new("Pods/#{file}").realpath.relative_path_from(target_dir_real_path)
+              Dir.chdir(target_dir) do
+                FileUtils.ln_sf(source, File.basename(file))
               end
             end
           end

lib/cocoapods/specification.rb

@@ -296,7 +296,7 @@ module Pod
     # methods.
     def header_search_paths
       dirs = [header_dir] + copy_header_mappings.keys
-      dirs.map { |dir| %{"Pods/Headers/#{dir}"} }
+      dirs.map { |dir| %{"$(POD_SRCROOT)/Headers/#{dir}"} }
     end
 
     def to_s

lib/cocoapods/xcodeproj_ext.rb

@@ -99,6 +99,7 @@ module Xcodeproj
     def self.build_settings(platform, scheme)
       settings = COMMON_BUILD_SETTINGS[:all].merge(COMMON_BUILD_SETTINGS[platform])
       settings['COPY_PHASE_STRIP'] = scheme == :debug ? 'NO' : 'YES'
+      settings['POD_SRCROOT'] = '$(SRCROOT)'
       if scheme == :debug
         settings.merge!(COMMON_BUILD_SETTINGS[:debug])
         settings['ONLY_ACTIVE_ARCH'] = 'YES' if platform == :osx