[libfuzzer] support of custom libfuzzer options via .options file.

testing/libfuzzer/tests/BUILD.gn

Index: testing/libfuzzer/tests/BUILD.gn
diff --git a/testing/libfuzzer/tests/BUILD.gn b/testing/libfuzzer/tests/BUILD.gn
index 7c74ffdec6c73beb80b1662ffb2ccfcfd6b2c953..550a52fcb9dac65233bfe0847583a517984587a5 100644
--- a/testing/libfuzzer/tests/BUILD.gn
+++ b/testing/libfuzzer/tests/BUILD.gn
@@ -12,7 +12,9 @@ test("libfuzzer_tests") {
     "fuzzer_launcher_test.cc",
   ]
   deps = [
+    ":test_dict_and_params_launcher.sh",
     ":test_dict_launcher.sh",
+    ":test_params_launcher.sh",
     "//base",
     "//testing/gmock",
     "//testing/gtest",
@@ -28,6 +30,17 @@ fuzzer_test_launcher("test_dict_launcher.sh") {
   dict = "test_dict"
 }
 
+fuzzer_test_launcher("test_params_launcher.sh") {
+  fuzzer_name = "print_args.py"
+  params = "-test_param=test_value"
+}
+
+fuzzer_test_launcher("test_dict_and_params_launcher.sh") {
+  fuzzer_name = "print_args.py"
+  dict = "test_dict"
+  params = "-test_param=test_value"
+}
+
 copy("print_args") {
   sources = [
     "print_args.py",