Make fuzz builds set SK_FUZZ_LOGGING

BUG=skia:5191
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1878363002

Review URL: https://codereview.chromium.org/1878363002
diff --git a/gyp/fuzz.gyp b/gyp/fuzz.gyp
index caca427..7290780 100644
--- a/gyp/fuzz.gyp
+++ b/gyp/fuzz.gyp
@@ -8,6 +8,9 @@
     'targets': [{
         'target_name': 'fuzz',
         'type': 'executable',
+        'defines': [
+          'SK_FUZZ_LOGGING',
+        ],
         'sources': [ '<!@(python find.py ../fuzz "*.cpp")' ],
         'dependencies': [
             'flags.gyp:flags',