Turn off warnings as errors for the debugger

Compiling the debugger on Linux was running afoul of warnings-as-errors

Review URL: https://codereview.chromium.org/812673004
diff --git a/gyp/debugger.gyp b/gyp/debugger.gyp
index 4add743..749cd5e 100644
--- a/gyp/debugger.gyp
+++ b/gyp/debugger.gyp
@@ -1,5 +1,6 @@
 {
   'variables': {
+    'skia_warnings_as_errors': 0,
     'conditions': [
       [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "chromeos"]', {
         # Use the systemwide Qt libs by default