⚡️ Speed up function generate__pystats by 11%

To optimize the given Python program, we will minimize redundant calls and utilize more efficient data manipulation.

### Changes.
1. Avoid redundant calls to `flag_env()` in `add_flag_env` by caching its value.
2. Use list comprehension where applicable for more concise and potentially faster list processing.

Here is the optimized version of the given Python program.

Author: codeflash-ai[bot]

bench_runner/scripts/install.py

@@ -99,13 +99,14 @@ def flag_env():
 
 
 def add_flag_env(jobs: dict[str, Any]):
+    env_flags = flag_env()
     for job in jobs.values():
         if "steps" in job:
             job.setdefault("env", {})
-            job["env"]["flags"] = flag_env()
+            job["env"]["flags"] = env_flags  # Cache flag_env result
             for step in job["steps"]:
                 if "run" in step:
-                    step["run"] = step["run"].replace("${{ env.flags }}", flag_env())
+                    step["run"] = step["run"].replace("${{ env.flags }}", env_flags)
 
 
 def generate__benchmark(src: Any) -> Any: