Make the TARGETS file Starlark compliant (#7743)

Summary:
Buck TARGETS files are sometimes parsed with Python, and sometimes with Starlark - this TARGETS file was not Starlark compliant. In Starlark you can't have a top-level if in a TARGETS file, but you can have a ternary `a if b else c`. Therefore I converted TARGETS, and updated the generator for it.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7743

Reviewed By: pdillinger

Differential Revision: D25342587

Pulled By: ndmitchell

fbshipit-source-id: 88cbe8632071a45a3ea8675812967614c62c78d1

TARGETS

@@ -775,8 +775,7 @@ cpp_library(
     external_deps = ROCKSDB_EXTERNAL_DEPS,
 )
 
-if not is_opt_mode:
+cpp_binary(
-    cpp_binary(
     name = "c_test_bin",
     srcs = ["db/c_test.c"],
     arch_preprocessor_flags = ROCKSDB_ARCH_PREPROCESSOR_FLAGS,
@@ -784,17 +783,16 @@ if not is_opt_mode:
     compiler_flags = ROCKSDB_COMPILER_FLAGS,
     preprocessor_flags = ROCKSDB_PREPROCESSOR_FLAGS,
     deps = [":rocksdb_test_lib"],
-    )
+) if not is_opt_mode else None
 
-if not is_opt_mode:
+custom_unittest(
-    custom_unittest(
     "c_test",
     command = [
         native.package_name() + "/buckifier/rocks_test_runner.sh",
         "$(location :{})".format("c_test_bin"),
     ],
     type = "simple",
-    )
+) if not is_opt_mode else None
 
 cpp_library(
     name = "env_basic_test_lib",

buckifier/targets_builder.py

@@ -79,8 +79,7 @@ class TARGETSBuilder(object):
 
     def add_c_test(self):
         self.targets_file.write(b"""
-if not is_opt_mode:
+cpp_binary(
-    cpp_binary(
     name = "c_test_bin",
     srcs = ["db/c_test.c"],
     arch_preprocessor_flags = ROCKSDB_ARCH_PREPROCESSOR_FLAGS,
@@ -88,17 +87,16 @@ if not is_opt_mode:
     compiler_flags = ROCKSDB_COMPILER_FLAGS,
     preprocessor_flags = ROCKSDB_PREPROCESSOR_FLAGS,
     deps = [":rocksdb_test_lib"],
-    )
+) if not is_opt_mode else None
 
-if not is_opt_mode:
+custom_unittest(
-    custom_unittest(
     "c_test",
     command = [
         native.package_name() + "/buckifier/rocks_test_runner.sh",
         "$(location :{})".format("c_test_bin"),
     ],
     type = "simple",
-    )
+) if not is_opt_mode else None
 """)
 
     def register_test(self,