Only pass -rdynamic when linking executables

-rdynamic only makes sense for dynamically linked executables, not shared libraries.

Bug: 1502880
Change-Id: I4f592ebbd508fa6b826964b86e9bda5a8c76042c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5037935
Auto-Submit: Arthur Eubanks <aeubanks@google.com>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Arthur Eubanks <aeubanks@google.com>
Cr-Commit-Position: refs/heads/main@{#1225698}

build/config/BUILDCONFIG.gn

@@ -342,7 +342,6 @@ default_compiler_configs = [
   "//build/config/compiler:default_optimization",
   "//build/config/compiler:default_stack_frames",
   "//build/config/compiler:default_symbols",
-  "//build/config/compiler:export_dynamic",
   "//build/config/compiler:no_exceptions",
   "//build/config/compiler:no_rtti",
   "//build/config/compiler:no_unresolved_symbols",
@@ -430,6 +429,7 @@ if (is_win) {
 
 # Executable defaults.
 default_executable_configs = default_compiler_configs + [
+                               "//build/config/compiler:export_dynamic",
                                "//build/config:default_libs",
                                "//build/config:executable_config",
                              ] + _linker_configs