[gn] do not hide symbols for monolithic build.

Otherwise dynamic linking with dlopen, as is the case with Node.js
addons, would not work.

R=fhinkel@chromium.org

Bug: v8:6105
Change-Id: I5a884afc003fdfdb9de7e9b0c736f1894ba0019a
Reviewed-on: https://chromium-review.googlesource.com/850112
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50384}

BUILD.gn

@@ -136,8 +136,6 @@ declare_args() {
   # while rolling in a new version of V8.
   v8_check_microtasks_scopes_consistency = ""
 
-  v8_monolithic = false
-
   # Enable mitigations for executing untrusted code.
   v8_untrusted_code_mitigations = true
 }

gni/v8.gni

@@ -45,6 +45,9 @@ declare_args() {
 
   # Use static libraries instead of source_sets.
   v8_static_library = false
+
+  # Enable monolithic static library for embedders.
+  v8_monolithic = false
 }
 
 if (v8_use_external_startup_data == "") {
@@ -97,7 +100,7 @@ if (v8_code_coverage && !is_clang) {
   ]
 }
 
-if (is_posix && v8_enable_backtrace) {
+if (is_posix && (v8_enable_backtrace || v8_monolithic)) {
   v8_remove_configs += [ "//build/config/gcc:symbol_visibility_hidden" ]
   v8_add_configs += [ "//build/config/gcc:symbol_visibility_default" ]
 }