CLI validates commands before checking -cc flag validity, resulting in "unknown command ''" #27868

Describe the bug

When passing an invalid C compiler via the -cc flag, the CLI evaluates the command/file arguments before validating if the requested C compiler actually exists. This leads to confusing error messages where the CLI complains about missing or invalid commands instead of the missing C compiler.

Reproduction Steps

No command provided

$ v -cc foo

Invalid command provided

$ v -cc foo bar

Valid command provided (only now does it check -cc)

$ v -cc foo -e 

Expected Behavior

When running v -cc foo, the compiler should validate the -cc argument early and immediately output:

builder error: C compiler 'foo' was requested with '-cc', but was not found.

Current Behavior

1. No command provided

$ v -cc foo
v: unknown command ``
Run  v help  for usage.

2. Invalid command provided

$ v -cc foo bar
v: unknown command `bar`.
Did you mean `share`?
Run  v help  for usage.

3. Valid command provided (only now does it check -cc)

$ v -cc foo -e
builder error: C compiler `foo` was requested with `-cc`, but was not found

Possible Solution

The validation for the -cc flag should be moved earlier in the execution pipeline, likely during the initial flag parsing. By checking if the requested C compiler exists immediately after the flag is consumed, the CLI can throw the correct builder error before the command router ever attempts to evaluate the remaining (or empty) arguments.

Additional Information/Context

No response

V version

V 0.5.2

Environment details (OS name and version, etc.)