Extract use_system_foo logic out of gyp files, patch 2

third_party/libusb/libusb.gyp

Index: third_party/libusb/libusb.gyp
diff --git a/third_party/libusb/libusb.gyp b/third_party/libusb/libusb.gyp
index 1e29d251a84f9139a2c01375ad9e45efc3225cdf..196054ecf4415db6c74751b46adc0af0e232c323 100644
--- a/third_party/libusb/libusb.gyp
+++ b/third_party/libusb/libusb.gyp
@@ -3,99 +3,68 @@
 # found in the LICENSE file.
 
 {
-  'variables': {
-    'use_system_libusb%': 0,
-  },
   'targets': [
     {
       'target_name': 'libusb',
+      'type': 'static_library',
+      'sources': [
+        'src/libusb/core.c',
+        'src/libusb/descriptor.c',
+        'src/libusb/io.c',
+        'src/libusb/sync.c',
+      ],
+      'include_dirs': [
+        'src',
+        'src/libusb',
+        'src/libusb/os',
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          'src/libusb',
+        ],
+      },
       'conditions': [
-        ['OS == "linux" and use_system_libusb==1', {
-          'type': 'none',
-          'variables': {
-            'headers_root_path': 'src/libusb',
-            'header_filenames': [
-              'libusb.h',
-            ],
-          },
-          'includes': [
-            '../../build/shim_headers.gypi',
+        [ 'OS == "linux" or OS == "android"', {
+          'sources': [
+            'src/libusb/os/linux_usbfs.c',
+            'src/libusb/os/threads_posix.c',
           ],
-          'direct_dependent_settings': {
-            'cflags': [
-              '<!@(pkg-config --cflags libusb-1.0)',
-            ],
-            'link_settings': {
-              'ldflags': [
-                '<!@(pkg-config --libs-only-L --libs-only-other libusb-1.0)',
-              ],
-              'libraries': [
-                '<!@(pkg-config --libs-only-l libusb-1.0)',
-              ],
-            },
-          },
-        }, {
-          'type': 'static_library',
+          'defines': [
+            'DEFAULT_VISIBILITY=',
+            'HAVE_POLL_H=1',
+            'HAVE_SYS_TIME_H=1',
+            'OS_LINUX=1',
+            'POLL_NFDS_TYPE=nfds_t',
+            'THREADS_POSIX=1',
+            '_GNU_SOURCE=1',
+          ],
+        }],
+        ['OS == "win"', {
           'sources': [
-            'src/libusb/core.c',
-            'src/libusb/descriptor.c',
-            'src/libusb/io.c',
-            'src/libusb/sync.c',
+            'src/libusb/os/poll_windows.c',
+            'src/libusb/os/threads_windows.c',
+            'src/libusb/os/windows_usb.c',
           ],
-          'include_dirs': [
+          'include_dirs!': [
             'src',
-            'src/libusb',
-            'src/libusb/os',
           ],
-          'direct_dependent_settings': {
-            'include_dirs': [
-              'src/libusb',
-            ],
-          },
-          'conditions': [
-            [ 'OS == "linux" or OS == "android"', {
-              'sources': [
-                'src/libusb/os/linux_usbfs.c',
-                'src/libusb/os/threads_posix.c',
-              ],
-              'defines': [
-                'DEFAULT_VISIBILITY=',
-                'HAVE_POLL_H=1',
-                'HAVE_SYS_TIME_H=1',
-                'OS_LINUX=1',
-                'POLL_NFDS_TYPE=nfds_t',
-                'THREADS_POSIX=1',
-                '_GNU_SOURCE=1',
-              ],
-            }],
-            ['OS == "win"', {
-              'sources': [
-                'src/libusb/os/poll_windows.c',
-                'src/libusb/os/threads_windows.c',
-                'src/libusb/os/windows_usb.c',
-              ],
-              'include_dirs!': [
-                'src',
-              ],
-              'include_dirs': [
-                'src/msvc',
-              ],
-            }],
-            ['OS == "mac"', {
-              'sources': [
-                'src/libusb/os/darwin_usb.c',
-                'src/libusb/os/threads_posix.c',
-              ],
-              'defines': [
-                'DEFAULT_VISIBILITY=',
-                'HAVE_POLL_H=1',
-                'HAVE_SYS_TIME_H=1',
-                'OS_DARWIN=1',
-                'POLL_NFDS_TYPE=nfds_t',
-                'THREADS_POSIX=1',
-                '_GNU_SOURCE=1',
-              ],
-            }],
+          'include_dirs': [
+            'src/msvc',
+          ],
+        }],
+        ['OS == "mac"', {
+          'sources': [
+            'src/libusb/os/darwin_usb.c',
+            'src/libusb/os/threads_posix.c',
+          ],
+          'defines': [
+            'DEFAULT_VISIBILITY=',
+            'HAVE_POLL_H=1',
+            'HAVE_SYS_TIME_H=1',
+            'OS_DARWIN=1',
+            'POLL_NFDS_TYPE=nfds_t',
+            'THREADS_POSIX=1',
+            '_GNU_SOURCE=1',
           ],
         }],
       ],