Combine rn_debug_flags and rn_feature_flags

Summary:
@public
Both of these are used for turning BUCK configs and build mode into compiler flags, so we should combine them to avoid confusion on where they are to be used.

Reviewed By: fkgozali

Differential Revision: D17262579

fbshipit-source-id: d145374fd619068f794018d79111720d30f6269c

React/CoreModules/BUCK

@@ -1,5 +1,5 @@
 load("@fbsource//tools/build_defs/apple:flag_defs.bzl", "OBJC_ARC_PREPROCESSOR_FLAGS", "get_debug_preprocessor_flags", "get_fbobjc_enable_exception_lang_compiler_flags_DEPRECATED")
-load("@fbsource//tools/build_defs/oss:rn_defs.bzl", "rn_apple_library", "rn_debug_flags")
+load("@fbsource//tools/build_defs/oss:rn_defs.bzl", "rn_apple_library", "rn_extra_build_flags")
 load(
     "@fbsource//xplat/configurations/buck/apple/plugins/sad_xplat_hosted_configurations:react_module_registration.bzl",
     "react_module_plugin_providers",
@@ -25,7 +25,7 @@ rn_apple_library(
         "-weak_framework",
         "WebKit",
     ],
-    exported_preprocessor_flags = rn_debug_flags(),
+    exported_preprocessor_flags = rn_extra_build_flags(),
     frameworks = [
         "Foundation",
         "UIKit",
@@ -61,7 +61,7 @@ rn_apple_library(
                   name = "PlatformConstants",
                   native_class_func = "RCTPlatformCls",
               ),
-    preprocessor_flags = OBJC_ARC_PREPROCESSOR_FLAGS + get_debug_preprocessor_flags() + rn_debug_flags() + [
+    preprocessor_flags = OBJC_ARC_PREPROCESSOR_FLAGS + get_debug_preprocessor_flags() + rn_extra_build_flags() + [
         "-DRN_DISABLE_OSS_PLUGIN_HEADER",
     ],
     reexport_all_header_dependencies = True,

tools/build_defs/oss/rn_defs.bzl

@@ -100,10 +100,7 @@ def react_native_dep(path):
 def react_native_xplat_dep(path):
     return "//ReactCommon/" + path
 
-def rn_debug_flags():
-    return []
-
-def rn_feature_flags():
+def rn_extra_build_flags():
     return []
 
 # React property preprocessor