Put config in sync between gyp and gn.

webrtc/base/base.gyp unconditionally set SSL_USE_OPENSSL and
HAVE_OPENSSL_SSL_H, fix webrtc/base/BUILD.gn to do the same.

Better implementation than https://codereview.webrtc.org/1441323002
to fix the same underlying issue (i.e. compilation on iOS).

BUG=459705

Review URL: https://codereview.webrtc.org/1812213002

Cr-Commit-Position: refs/heads/master@{#12078}

webrtc/base/BUILD.gn

@@ -190,11 +190,13 @@ static_library("rtc_base") {
 
   configs += [
     "..:common_config",
+    ":openssl_config",
     ":rtc_base_config",
   ]
 
   public_configs = [
     "..:common_inherited_config",
+    ":openssl_config",
     ":rtc_base_config",
   ]
 
@@ -485,7 +487,6 @@ static_library("rtc_base") {
   }
 
   if (use_openssl) {
-    public_configs += [ ":openssl_config" ]
     if (rtc_build_ssl) {
       deps += [ "//third_party/boringssl" ]
     } else {