build: Specify full path to the grep utility in rvcmd.sh

[mcoliver]

some people have grep aliased to something else like rg which uses -E differently. Specifying the full path to the grep bin ensures we are using the right utility.

Linked issues

Fixes #1092

Summarize your change.

Full pathname to grep utility

Describe the reason for the change.

It's great that if the build fails it attempts to grep for things like errors. The issue is that sometime people (like me) have grep aliased to something like ripgrep or silver searcher (ag) which sometimes use flags differently. For example -E is different in gnu grep and ripgrep. Referencing the tool with the full pathname to ensure we are using /usr/bin/grep would be more deterministic.

Describe what you have tested and on which operating system.

macos

Add a list of changes, and note any that might need special attention during the review.

If possible, provide screenshots.

[Copilot]

Pull request overview

This PR updates all grep invocations in rvcmds.sh to use the full path /usr/bin/grep instead of relying on the shell's PATH resolution. This prevents issues when users have grep aliased to alternative tools like ripgrep or ag, which may interpret flags differently (e.g., the -E flag).

Changes:

• Updated all grep commands to use absolute path /usr/bin/grep
• Changes span shell detection, hook installation, build error filtering, and user-facing help messages

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[mcoliver]

Updated to use command as per co-pilot