Ensure consistent configuration and output directory (#7)

If an app (`ios_application`) depends on a library (`apple_framework`), when building the app and the library separately, the libraries will be built twice into different directories. This is because of transition which causes different configurations. A thorough discussion can be found here.

This change ensures when building the app and the library, they will have same transition, thus they will have the same configuration and same output directory.

We can verify this by running `bazel cquery //ios/foundations/StringFoundation:StringFoundation --universe_scope=//ios/foundations/StringFoundation:StringFoundation,//ios:AirbnbApp` to make sure only one configuration is showing up.

This change requires to have `--experimental_output_directory_naming_scheme=diff_against_baseline` flag set.

rules/transition_support.bzl

@@ -105,7 +105,7 @@ def _apple_rule_transition_impl(settings, attr):
     ret = {
         "//command_line_option:apple configuration distinguisher": "applebin_" + platform_type,
         "//command_line_option:apple_platform_type": platform_type,
-        "//command_line_option:apple_split_cpu": settings["//command_line_option:apple_split_cpu"],
+        "//command_line_option:apple_split_cpu": ios_multi_cpus,
         "//command_line_option:compiler": settings["//command_line_option:apple_compiler"] if _supports_clo_apple_compiler else None,
         "//command_line_option:cpu": cpu_string,
         "//command_line_option:crosstool_top": (
@@ -118,6 +118,7 @@ def _apple_rule_transition_impl(settings, attr):
         "//command_line_option:macos_minimum_os": _min_os_version_or_none(attr, attr_platforms, "macos", platform_type),
         "//command_line_option:tvos_minimum_os": _min_os_version_or_none(attr, attr_platforms, "tvos", platform_type),
         "//command_line_option:watchos_minimum_os": _min_os_version_or_none(attr, attr_platforms, "watchos", platform_type),
+        "//command_line_option:minimum_os_version": _min_os_version_or_none(attr, attr_platforms, "ios", platform_type),
     }
     return ret
 
@@ -169,6 +170,7 @@ _apple_rule_transition = transition(
         "//command_line_option:macos_minimum_os",
         "//command_line_option:tvos_minimum_os",
         "//command_line_option:watchos_minimum_os",
+        "//command_line_option:minimum_os_version",
     ],
 )