Node.js used by sfdx-cli/8.89.2 does not support Windows 7 by default #898

Summary
The recent update which was automatically pushed includes updating Node.js to v14.15.4. Since this version of Node.js does not support Windows 7, it made SFDX unusable for Windows 7 users without some hack.

When running SFDX, Windows 7 users will get the error:
Node.js is only supported on Windows 8.1, Windows Server 2012 R2, or higher. Setting the NODE_SKIP_PLATFORM_CHECK environment variable to 1 skips this check, but Node.js might not execute correctly. Any issues encountered on unsupported platforms will not be fixed.12:30:07.195

We weren't notified that Salesforce CLI will no longer support Windows 7. The documentation from salesforce mentions "Windows—Windows 7 (64-bit and 32-bit) or later" as the System requirements, so we do expect it to still work without us having to modify the sfdx.cmd file.

Steps To Reproduce:

1. Using a windows 7 machine, install the latest version of Salesforce CLI
2. Run sfdx -v

Expected result
Command is executed, and the version is returned.

Actual result
Error message given:
Node.js is only supported on Windows 8.1, Windows Server 2012 R2, or higher. Setting the NODE_SKIP_PLATFORM_CHECK environment variable to 1 skips this check, but Node.js might not execute correctly. Any issues encountered on unsupported platforms will not be fixed.12:30:07.195

Additional information
SFDX CLI Version(to find the version of the CLI engine run sfdx --version):
sfdx-cli/7.89.2-d1d2614d02 win32-x64 node-v14.15.4

SFDX plugin Version(to find the version of the CLI plugin run sfdx plugins --core):
@oclif/plugin-autocomplete 0.3.0 (core)
@oclif/plugin-commands 1.3.0 (core)
@oclif/plugin-help 3.2.2 (core)
@oclif/plugin-not-found 1.2.4 (core)
@oclif/plugin-plugins 1.9.5 (core)
@oclif/plugin-update 1.4.0-2 (core)
@oclif/plugin-warn-if-update-available 1.7.0 (core)
@oclif/plugin-which 1.0.3 (core)
@salesforce/sfdx-trust 3.6.0 (core)
alias 1.1.5 (core)
auth 1.4.8 (core)
config 1.2.4 (core)
etcopydata 0.5.7
generator 1.1.5 (core)
salesforcedx 51.1.1 (core)
├─ limits 1.0.4 (core)
├─ schema 1.0.4 (core)
├─ custom-metadata 1.0.11 (core)
├─ templates 51.3.0 (core)
├─ apex 0.1.4 (core)
├─ user 1.1.2 (core)
├─ salesforce-alm 51.1.1 (core)
└─ @salesforce/sfdx-plugin-lwc-test 0.1.7 (core)
sfdmu 3.9.4
sfdx-cli 7.89.2 (core)
telemetry 1.1.1 (core)

OS and version:
Windows 7