Add configurable max_jobs parameter to compute_fbank_librispeech.py

[redsheep913]

Problem

• In compute_fbank_librispeech.py, the number of parallel jobs was hardcoded to 80 (num_jobs=num_jobs if ex is None else 80)
• This can lead to system resource exhaustion on machines with limited capacity
• No way to configure the maximum number of concurrent processes

Solution

• Added a new command-line parameter --max_jobs to control the maximum number of parallel processes
• Replaced the hardcoded value with this configurable parameter
• Set a reasonable default to prevent resource exhaustion

Implementation

• Added parameter parsing for --max_jobs in the argument parser
• Used this parameter instead of the hardcoded value 80
• Ensured backward compatibility with existing scripts

Benefits

• Improved resource utilization efficiency
• Prevents system crashes due to excessive parallelization
• Enhances script flexibility across different hardware environments

Testing

• Tested with various max_jobs values on local environment
• Confirmed reasonable system resource usage
• Functionality works as expected with no performance degradation

[csukuangfj]

Can you leave this block unchanged? The original one is shorter and easier to follow.