Make iOS main() functions normal.

The weird foo_mains are no longer needed when we build with GN.

CQ_INCLUDE_TRYBOTS=skia.primary:Build-Mac-Clang-arm-Debug-iOS

Change-Id: Iae50696741e0dc277d96dda4968a1ae41cb17c8a
Reviewed-on: https://skia-review.googlesource.com/8064
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Stephan Altmueller <stephana@google.com>
diff --git a/tools/skdiff/skdiff_image.cpp b/tools/skdiff/skdiff_image.cpp
index 287523d..cb446d4 100644
--- a/tools/skdiff/skdiff_image.cpp
+++ b/tools/skdiff/skdiff_image.cpp
@@ -111,8 +111,7 @@
 const int kNoError = 0;
 const int kGenericError = -1;
 
-int tool_main(int argc, char** argv);
-int tool_main(int argc, char** argv) {
+int main(int argc, char** argv) {
     DiffMetricProc diffProc = compute_diff_pmcolor;
 
     // Maximum error tolerated in any one color channel in any one pixel before
@@ -366,9 +365,3 @@
 
     return num_failing_results;
 }
-
-#if !defined SK_BUILD_FOR_IOS
-int main(int argc, char * const argv[]) {
-    return tool_main(argc, (char**) argv);
-}
-#endif