[LPM] Speculative fix for ClusterFuzz Mac build bot breakage

Don't do ClusterFuzz builds of targets dependant on fuzzable_proto_library when not on Linux.

Bug: 869035, 769578
Change-Id: Ic872263c117a2ef63ab4552d0b5d9f200311aed0
Reviewed-on: https://chromium-review.googlesource.com/1155485
Commit-Queue: Jonathan Metzman <metzman@chromium.org>
Reviewed-by: Martin Barbella <mbarbella@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579127}

third_party/libprotobuf-mutator/fuzzable_proto_library.gni

+import("//testing/libfuzzer/fuzzer_test.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 template("fuzzable_proto_library") {
@@ -37,6 +38,14 @@ template("fuzzable_proto_library") {
         "//third_party/libprotobuf-mutator:protobuf_full",
       ]
     }
+
+    # Don't bother doing builds for CF if we aren't on Linux because of build
+    # breakages on Mac.
+    # TODO(crbug.com/869035): Figure out what is causing this issue and fix
+    # instead of working around it.
+    if (!is_linux) {
+      all_dependent_configs = [ "//testing/libfuzzer:no_clusterfuzz" ]
+    }
   } else {
     # fuzzable_proto_library should behave like a proto_library when
     # !use_libfuzzer.