patch: restore output from failed patch

[cho-m]

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Before #18613, we used safe_system which would print stderr by default. After switching to Utils.safe_popen_write, stderr/stdout is captured in the exception and discarded.

This had caused some confusion in PRs as the resulting logs don't clearly explain failure.

Current brew output looks like:

==> Patching
==> Applying b6cf2e7222c24343b868986e867ddb7adad0bf30.patch

READ THIS: https://docs.brew.sh/Troubleshooting

With change, the output is shown to user, e.g.

==> Patching
==> Applying b6cf2e7222c24343b868986e867ddb7adad0bf30.patch
Error: Failure while executing; `patch -g 0 -f -p1` exited with 1. Here's the output:
patching file 'src/fastnetmon.cpp'
2 out of 2 hunks failed--saving rejects to 'src/fastnetmon.cpp.rej'
patching file 'src/fastnetmon_api_client.cpp'
2 out of 2 hunks failed--saving rejects to 'src/fastnetmon_api_client.cpp.rej'

READ THIS: https://docs.brew.sh/Troubleshooting

[MikeMcQuaid]

Makes sense, thanks!