fix: prevent IDL generation when compilation fails

[bytehash69]

Problem

When anchor build is run, if program compilation fails, the build process
would still attempt to generate IDLs. This is wasteful because:

• IDL generation requires successfully compiled programs
• It produces confusing error messages
• Mirrors the logical dependency: compile → then generate IDL

Solution

Add early exit in _build_rust_cwd function when compilation fails,
preventing IDL generation from being attempted.

Changes

• Added explicit check for compilation success before IDL generation
• Return error immediately when cargo build-sbf fails
• IDL generation now only runs after confirmed successful compilation

Related

• Respects the logical flow: anchor build --no-idl → anchor idl build

closes #4056

[vercel]

@bytehash69 is attempting to deploy a commit to the Solana Foundation Team on Vercel.

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[jamie-osec]

if program compilation fails, the build process would still attempt to generate IDLs

Can you explain how to reproduce this situation? Invoking anchor build in a program with code containing errors reports the error and stops, it does not seem to attempt to build the IDL (unless anchor idl build) is explicitly requested.

[jamie-osec]

Also, the change here doesn't seem to match the PR description. It just makes anchor build --verifiable respect --no-idl, and a failed build propagate the error instead of immediately exiting.