chore(tools): cache icon builds

[nnaydenow]

Implement a caching mechanism for icon packages so they are regenerated only when there are changes in the icon packages or in the @ui5/webcomponents-tools package. This will reduce local build times when testing and also speed up the startup of the development server.

[Copilot]

Pull Request Overview

This PR implements a caching mechanism for icon packages to reduce build times by only regenerating icons when there are actual changes in the icon packages or the @ui5/webcomponents-tools package.

• Adds a new hashing utility that tracks file changes using FNV-1a hash algorithm combined with modification times
• Integrates hash checking into the icon build process to skip builds when no changes are detected
• Updates build scripts to save and check hashes before performing expensive regeneration operations

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 5 comments.

File	Description
packages/tools/package.json	Adds ignore dependency for .gitignore file parsing
packages/tools/lib/icons-hash/index.mjs	New utility for computing and comparing file hashes to detect changes
packages/tools/icons-collection/nps.js	Updates build scripts to check hashes before building and save hashes after building

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[Copilot]

Empty catch block silently ignores all errors. Consider adding a comment explaining why errors are intentionally ignored, or handle specific expected errors like ENOENT.

Suggested change

	} catch { }
	} catch (err) {
	// Ignore missing .gitignore files, but log other errors
	if (err.code !== 'ENOENT') {
	console.error(`Error accessing ${candidate}:`, err);
	}
	}

[Copilot]

Using process.exit() makes the code harder to test and reuse. Consider throwing an error or returning a status code that the caller can handle.

Suggested change

	process.exit(1);
	// Indicate missing hashes with a specific error
	throw new Error("NO_HASHES_FOUND");

[Copilot]

Using process.exit() makes the code harder to test and reuse. Consider throwing an error or returning a status code that the caller can handle.

[Copilot]

Using process.exit() makes the code harder to test and reuse. Consider throwing an error or returning a status code that the caller can handle.

Suggested change

	process.exit(1);
	throw new Error("Usage: node hashes.js <save|check>");

[Copilot]

Empty catch block silently ignores all errors. Consider adding a comment explaining why errors are intentionally ignored, or handle specific expected errors like file not found.

Suggested change

	process.exit(1);
	} catch (err) {
	if (err && err.code === "ENOENT") {
	console.log(`No build hashes found for the ${getRepoName(repoPath)} package. Building it now.`);
	process.exit(1);
	} else {
	console.error(`Error reading build hashes for the ${getRepoName(repoPath)} package:`, err);
	process.exit(2);
	}