Revert of Run pkg-config for Udev only if use_udev==1 (patchset #1 of...

Revert of Run pkg-config for Udev only if use_udev==1 (patchset #1 of https://codereview.chromium.org/429723002/)

Reason for revert:
Breaks builds where use_udev==0 since certain targets just assume udev and never check against use_udev.

Udev package should be wrapped in a use_udev confitional altogether and all the locations using Udev should check against use_udev.

Original issue's description:
> Run pkg-config for Udev only if use_udev==1
> 
> Some embedded platforms do not have udev support. The change will skip
> running pkg-config if use_udev=0.
> 
> BUG=none
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=288770

TBR=brettw@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/469763002

Cr-Commit-Position: refs/heads/master@{#289280}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289280 0039d316-1c4b-4281-b951-d872f2087c98

build/config/linux/BUILD.gn

@@ -47,10 +47,8 @@ pkg_config("pangoft2") {
   packages = [ "pangoft2" ]
 }
 
-if (use_udev) {
-  pkg_config("udev") {
-    packages = [ "libudev" ]
-  }
+pkg_config("udev") {
+  packages = [ "libudev" ]
 }
 
 # Note: if your target also depends on //dbus, you don't need to add this

build/linux/system.gyp

@@ -1037,7 +1037,7 @@
       'type': 'none',
       'conditions': [
         # libudev is not available on *BSD
-        ['_toolset=="target" and os_bsd!=1 and use_udev==1', {
+        ['_toolset=="target" and os_bsd!=1', {
           'direct_dependent_settings': {
             'cflags': [
               '<!@(<(pkg-config) --cflags libudev)'