Compile pdf viewer manaully only, disable on build bots.

gyp/most.gyp

 # Build ALMOST everything provided by Skia; this should be the default target.
 #
 # This omits the following targets that many developers won't want to build:
 # - debugger: this requires QT to build
 #
 {
   'targets': [
     {
       'target_name': 'most',
       'type': 'none',
       'dependencies': [
         # The minimal set of static libraries for basic Skia functionality.
         'skia_lib.gyp:skia_lib',
 
         'bench.gyp:bench',
         'gm.gyp:gm',
         'SampleApp.gyp:SampleApp',
         'tests.gyp:tests',
         'tools.gyp:tools',
         'pathops_unittest.gyp:*',
+#       'pdfviewer.gyp:pdfviewer',
       ],
       'conditions': [
         ['skia_os == "android"', {
           'dependencies': [ 'android_system.gyp:SkiaAndroidApp' ],
         }],
-        ['skia_os == "linux"', {
-          'dependencies': [ 'pdfviewer.gyp:pdfviewer' ],
-        }],
       ],
     },
   ],
 }
 
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