pw_fuzzer: Don't build if unsupported

When fuzzing is not supported, pw_fuzzer creates a unit test target with
a couple pre-canned test inputs. Some devices can't fit the requested
buffer size provided for fuzz testing, and it's unlikely these fuzz
tests will be run on devices anyway.

For now, completely disable building pw_fuzzer tests on targets that
don't support fuzzing.

Bug: 195
Change-Id: I4e7eb0bf6d3fa0e064d8a1541600b9243e39a72d
diff --git a/pw_fuzzer/fuzzer.gni b/pw_fuzzer/fuzzer.gni
index a5e326b..f108fef 100644
--- a/pw_fuzzer/fuzzer.gni
+++ b/pw_fuzzer/fuzzer.gni
@@ -69,6 +69,9 @@
   } else {
     # Build a unit test that exercise the fuzz target function.
     pw_test(target_name) {
+      # TODO(pwbug/195): Re-enable when there's better configurability for
+      # on-device fuzz testing.
+      enable_if = false
       sources = []
       configs = []
       deps = []