Allow overriding maxBuffer when compiling with Dockerized solc

[coeniebeyers]

• I've asked for help in the Truffle Gitter before filing this issue.

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Issue

Exactly like #3140, however 1024 * 1024 * 100 isn't enough for our instrumented files when we are trying to produce coverage reports.

Steps to Reproduce

Run truffle coverage.

Expected Behavior

Coverage to run.

Actual Results

We're getting the same error as in https://app.circleci.com/pipelines/github/trufflesuite/truffle/184/workflows/81f7c350-d718-46f8-8450-9f941a592cc6/jobs/79:

Error: spawnSync /bin/sh ENOBUFS
    at Object.spawnSync (internal/child_process.js:1002:20)
    at spawnSync (child_process.js:614:24)
    at execSync (child_process.js:661:13)
    at Object.compile (/home/circleci/project/node_modules/truffle/build/webpack:/packages/compile-solidity/compilerSupplier/loadingStrategies/Docker.js:23:1)
    at invokeCompiler (/home/circleci/project/node_modules/truffle/build/webpack:/packages/compile-solidity/run.js:257:1)

Environment

• Operating System: Ubuntu 20.04
• Ethereum client: Ganache
• Truffle version (truffle version): 5.1.37
• node version (node --version): 12.18.3
• npm version (npm --version): 6.14.6

Could we change maxBuffer for the docker loading strategy to be set via environment variable?