Improvements for OSX build (#13201)

* Hide some helper variables as internal ones

* Added an ability to test private API for TF FE

* OSX improvements

* Fixed project generation for xcode

cmake/developer_package/IEDevScriptsConfig.cmake

@@ -79,6 +79,11 @@ if(NOT COMMAND find_host_package)
         find_package(${ARGN})
     endmacro()
 endif()
+if(NOT COMMAND find_host_library)
+    macro(find_host_library)
+        find_library(${ARGN})
+    endmacro()
+endif()
 if(NOT COMMAND find_host_program)
     macro(find_host_program)
         find_program(${ARGN})

cmake/developer_package/ncc_naming_style/ncc_naming_style.cmake

@@ -56,13 +56,23 @@ endif()
 # Since we were able to find_package(Clang) in a separate process
 # let's try to find in current process
 if(ENABLE_NCC_STYLE)
-    find_host_package(Clang QUIET)
+    if(APPLE)
+        find_host_library(libclang_location NAMES clang
+                          PATHS /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib
+                          DOC "Path to clang library")
+    else()
+        find_host_package(Clang QUIET)
+    endif()
+
     if(Clang_FOUND AND TARGET libclang)
         get_target_property(libclang_location libclang LOCATION)
-        message(STATUS "Found libclang: ${libclang_location}")
-    else()
+    endif()
+
+    if(NOT libclang_location)
         message(WARNING "clang-${clang_version} libclang-${clang_version}-dev are not found (required for ncc naming style check)")
         set(ENABLE_NCC_STYLE OFF)
+    else()
+        message(STATUS "Found libclang: ${libclang_location}")
     endif()
 endif()