try always setting fvisibility=hidden

It simplifies things to always build this way, to mimic how we're built
by clients, and to better approximate MSVC defaults.  I'm not sure I
believe my old note about making stack traces worse on Linux.

Change-Id: I0554a58573074fc6ae030fa09e11976a718645b5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307834
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

Author: Mike Klein

gn/BUILD.gn

@@ -133,15 +133,12 @@ config("default") {
     cflags += [
       "-fstrict-aliasing",
       "-fPIC",
+      "-fvisibility=hidden",
+    ]
+    cflags_cc += [
+      "-std=c++17",
+      "-fvisibility-inlines-hidden",
     ]
-    cflags_cc += [ "-std=c++17" ]
-
-    # The main idea is to slim the exported API, but these flags also improve link time on Mac.
-    # These would make stack traces worse on Linux, so we don't just set them willy-nilly.
-    if (is_component_build || is_ios || is_mac) {
-      cflags += [ "-fvisibility=hidden" ]
-      cflags_cc += [ "-fvisibility-inlines-hidden" ]
-    }
   }
 
   if (current_cpu == "arm") {