Set -DROCKSDB_JEMALLOC for buck build if jemalloc presents (#4489)

Summary:
Set the macro if default allocator is jemalloc. It doesn't handle the case when allocator is specified, e.g.
```
cpp_binary(
    name="xxx"
    allocator="jemalloc", # or "malloc" or something else
    deps=["//rocksdb:rocksdb"],
)
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4489

Differential Revision: D10363683

Pulled By: yiwu-arbug

fbshipit-source-id: 5da490336a8e78e0feb0900c29e8036e7ec6f12b

TARGETS

@@ -67,6 +67,16 @@ is_opt_mode = build_mode.startswith("opt")
 if is_opt_mode:
     rocksdb_compiler_flags.append("-DNDEBUG")
 
+default_allocator = read_config("fbcode", "default_allocator")
+
+sanitizer = read_config("fbcode", "sanitizer")
+
+# Let RocksDB aware of jemalloc existence.
+# Do not enable it if sanitizer presents.
+if default_allocator.startswith("jemalloc") and sanitizer == "":
+    rocksdb_compiler_flags.append("-DROCKSDB_JEMALLOC")
+    rocksdb_external_deps.append(("jemalloc", None, "headers"))
+
 cpp_library(
     name = "rocksdb_lib",
     srcs = [

buckifier/targets_cfg.py

@@ -70,6 +70,16 @@ is_opt_mode = build_mode.startswith("opt")
 # doesn't harm and avoid forgetting to add it.
 if is_opt_mode:
     rocksdb_compiler_flags.append("-DNDEBUG")
+
+default_allocator = read_config("fbcode", "default_allocator")
+
+sanitizer = read_config("fbcode", "sanitizer")
+
+# Let RocksDB aware of jemalloc existence.
+# Do not enable it if sanitizer presents.
+if default_allocator.startswith("jemalloc") and sanitizer == "":
+    rocksdb_compiler_flags.append("-DROCKSDB_JEMALLOC")
+    rocksdb_external_deps.append(("jemalloc", None, "headers"))
 """