fix(gatsby): [rendering engines] use results of exports removal if sourceMap was not generated alongside transformed code

[pieh]

Description

We use custom loader to remove gatsby-node lifecycles that are not relevant to engines runtime in

gatsby/packages/gatsby/src/schema/graphql-engine/bundle-webpack.ts

Lines 114 to 131 in 86e1685

	{
	// specific set of loaders for gatsby-node files - our babel transform that removes lifecycles not needed for engine -> relocator
	test: /gatsby-node\.(cjs|mjs|js|ts)$/,
	// it is recommended for Node builds to turn off AMD support
	parser: { amd: false },
	use: [
	assetRelocatorUseEntry,
	{
	loader: require.resolve(
	`../../utils/webpack/loaders/webpack-remove-exports-loader`
	),
	options: {
	remove: getApisToRemoveForQueryEngine(),
	jsx: false,
	},
	},
	],
	},

This however is currently not always working as expected as the loader currently expect sourceMap to be generated alongside transformed code before using the transformed code. If map is not generated we discard transformed code.

This PR allow usage of transformed code if it's not accompanied by sourcemap - we will only do passthrough if transformed code is not generated.

Documentation

Related Issues

[pieh]

changes in packages/gatsby/src/schema/graphql-engine/standalone-regenerate.ts are unrelated to fix itself, just some dev tools update that I did as part of my investigation that I think make sense to commit in general - I can drop this change from this PR (and either create separate or just skip pushing it)

[pieh]

Actual fix here - sometimes we will get result.code with falsyt result.map, this change make sure we use that and only fallback to pass original source (and sourceMap) if transformed code is falsy or we get no result at all (not sure if that can ever happen without error)