Exclude c_test from buck build opt mode (#7093)

Summary:
Fix a Facebook internal build

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7093

Test Plan:
buck build mode/opt :c_test :c_test_bin (was compilation
failure, now "not found")
buck build mode/dev :c_test :c_test_bin (still passes)

Reviewed By: ajkr

Differential Revision: D22412528

Pulled By: pdillinger

fbshipit-source-id: 8e55c43dbf95386597e4cc690c41d9cbdcee03aa

TARGETS

@@ -449,7 +449,8 @@ cpp_library(
     external_deps = ROCKSDB_EXTERNAL_DEPS,
 )
 
-cpp_binary(
+if not is_opt_mode:
+    cpp_binary(
         name = "c_test_bin",
         srcs = ["db/c_test.c"],
         arch_preprocessor_flags = ROCKSDB_ARCH_PREPROCESSOR_FLAGS,
@@ -457,16 +458,17 @@ cpp_binary(
         compiler_flags = ROCKSDB_COMPILER_FLAGS,
         preprocessor_flags = ROCKSDB_PREPROCESSOR_FLAGS,
         deps = [":rocksdb_test_lib"],
-)
+    )
 
-custom_unittest(
+if not is_opt_mode:
+    custom_unittest(
         "c_test",
         command = [
             native.package_name() + "/buckifier/rocks_test_runner.sh",
             "$(location :{})".format("c_test_bin"),
         ],
         type = "simple",
-)
+    )
 
 cpp_library(
     name = "env_basic_test_lib",

buckifier/targets_builder.py

@@ -78,7 +78,8 @@ class TARGETSBuilder(object):
 
     def add_c_test(self):
         self.targets_file.write("""
-cpp_binary(
+if not is_opt_mode:
+    cpp_binary(
         name = "c_test_bin",
         srcs = ["db/c_test.c"],
         arch_preprocessor_flags = ROCKSDB_ARCH_PREPROCESSOR_FLAGS,
@@ -86,16 +87,17 @@ cpp_binary(
         compiler_flags = ROCKSDB_COMPILER_FLAGS,
         preprocessor_flags = ROCKSDB_PREPROCESSOR_FLAGS,
         deps = [":rocksdb_test_lib"],
-)
+    )
 
-custom_unittest(
+if not is_opt_mode:
+    custom_unittest(
         "c_test",
         command = [
             native.package_name() + "/buckifier/rocks_test_runner.sh",
             "$(location :{})".format("c_test_bin"),
         ],
         type = "simple",
-)
+    )
 """)
 
     def register_test(self,