Provide a way to disable libpci dependency.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 708e12c2aa3f6ae9ff536f5c7a71f33ca6d4f34f..dcecfd53f07c4b8e778d5b182130e9edec9545d8 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -61,6 +61,9 @@
           # Whether we are using Views Toolkit
           'toolkit_views%': 0,
 
+          # Use the PCI lib to collect GPU information.
+          'use_libpci%': 1,
+
           # Use OpenSSL instead of NSS as the underlying SSL and crypto
           # implementation. Certificate verification will in most cases be
           # handled by the OS. If OpenSSL's struct X509 is used to represent
@@ -136,6 +139,7 @@
         'use_cras%': '<(use_cras)',
         'use_ozone%': '<(use_ozone)',
         'embedded%': '<(embedded)',
+        'use_libpci%': '<(use_libpci)',
         'use_openssl%': '<(use_openssl)',
         'use_openssl_certs%': '<(use_openssl_certs)',
         'enable_viewport%': '<(enable_viewport)',
@@ -281,6 +285,7 @@
       'use_aura%': '<(use_aura)',
       'use_ash%': '<(use_ash)',
       'use_cras%': '<(use_cras)',
+      'use_libpci%': '<(use_libpci)',
       'use_ozone%': '<(use_ozone)',
       'use_ozone_evdev%': '<(use_ozone_evdev)',
       'use_clipboard_aurax11%': '<(use_clipboard_aurax11)',
@@ -1073,6 +1078,7 @@
     'use_aura%': '<(use_aura)',
     'use_ash%': '<(use_ash)',
     'use_cras%': '<(use_cras)',
+    'use_libpci%': '<(use_libpci)',
     'use_openssl%': '<(use_openssl)',
     'use_openssl_certs%': '<(use_openssl_certs)',
     'use_nss%': '<(use_nss)',
@@ -2935,6 +2941,9 @@
       }],
     ],  # conditions for 'target_defaults'
     'target_conditions': [
+      ['<(use_libpci)==1', {
+        'defines': ['USE_LIBPCI=1'],
+      }],
       ['<(use_openssl)==1', {
         'defines': ['USE_OPENSSL=1'],
       }],