Support building BoringSSL with NSS certificates.

build/linux/system.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'conditions': [
       ['sysroot!=""', {
         'pkg-config': '<(chroot_cmd) ./pkg-config-wrapper "<(sysroot)" "<(target_arch)" "<(system_libdir)"',
       }, {
@@ skipping 1162 matching lines @@
     {
       'target_name': 'ssl',
       'type': 'none',
       'conditions': [
         ['_toolset=="target"', {
           'conditions': [
             ['use_openssl==1', {
               'dependencies': [
                 '../../third_party/boringssl/boringssl.gyp:boringssl',
               ],
-            }],
-            ['use_openssl==0', {
+            }, {
               'dependencies': [
                 '../../net/third_party/nss/ssl.gyp:libssl',
               ],
               'direct_dependent_settings': {
                 'include_dirs+': [
                   # We need for our local copies of the libssl3 headers to come
                   # before other includes, as we are shadowing system headers.
                   '<(DEPTH)/net/third_party/nss/ssl',
                 ],
+              },
+            }],
+            # Link in the system NSS if it is used for either the internal
+            # crypto library (use_openssl==0) or platform certificate
+            # library (use_nss_certs==1).
+            ['use_openssl==0 or use_nss_certs==1', {
+              'direct_dependent_settings': {
                 'cflags': [
                   '<!@(<(pkg-config) --cflags nss)',
                 ],
               },
               'link_settings': {
                 'ldflags': [
                   '<!@(<(pkg-config) --libs-only-L --libs-only-other nss)',
                 ],
                 'libraries': [
                   '<!@(<(pkg-config) --libs-only-l nss | sed -e "s/-lssl3//")',
                 ],
               },
-            }],
-            ['use_openssl==0 and clang==1', {
-              'direct_dependent_settings': {
-                'cflags': [
-                  # There is a broken header guard in /usr/include/nss/secmod.h:
-                  # https://bugzilla.mozilla.org/show_bug.cgi?id=884072
-                  '-Wno-header-guard',
-                ],
-              },
+              'conditions': [
+                ['clang==1', {
+                  'direct_dependent_settings': {
+                    'cflags': [
+                      # There is a broken header guard in /usr/include/nss/secmod.h:
+                      # https://bugzilla.mozilla.org/show_bug.cgi?id=884072
+                      '-Wno-header-guard',
+                    ],
+                  },
+                }],
+              ],
             }],
           ]
         }],
       ],
     },
   ],
 }