chore(gatsby-cli): delete *.d.ts files before creating new ones

[pieh]

Description

#24381 introduced chain where gatsby-cli source files try to use build gatsby-cli files:

• gatsby/packages/gatsby-cli/src/reporter/loggers/ink/context.tsx

  Line 3 in 96dbf2b

  import { IGatsbyState } from "gatsby/src/redux/types"

• gatsby/packages/gatsby/src/redux/types.ts

  Line 7 in 96dbf2b

  import { ITypeMetadata } from "../schema/infer/inference-metadata"

• gatsby/packages/gatsby/src/schema/infer/inference-metadata.ts

  Line 64 in 96dbf2b

  import { TypeConflictReporter } from "./type-conflict-reporter"

• gatsby/packages/gatsby/src/schema/infer/type-conflict-reporter.ts

  Line 2 in 96dbf2b

  import report from "gatsby-cli/lib/reporter"

This weirdly doesn't cause issues other than tsc errors when trying to build already built package and it manifest with errors like these:

$ cross-env NODE_ENV=production npm run build && npm run typegen
npm WARN lifecycle The node binary used for scripts is /var/folders/7b/7_tqb8f50bx7jhyj0bn9r8v80000gn/T/yarn--1592386922492-0.026473074778530892/node but npm is using /Users/misiek/.nvm/versions/node/v10.16.3/bin/node itself. Use the `--scripts-prepend-node-path` option to include the path for the node binary npm was executed with.
> gatsby-cli@2.12.46 build /Users/misiek/dev/gatsby/packages/gatsby-cli
> babel src --out-dir lib --ignore "**/__tests__" --extensions ".ts,.js,.tsx"
Successfully compiled 43 files with Babel (2010ms).
npm WARN lifecycle The node binary used for scripts is /var/folders/7b/7_tqb8f50bx7jhyj0bn9r8v80000gn/T/yarn--1592386922492-0.026473074778530892/node but npm is using /Users/misiek/.nvm/versions/node/v10.16.3/bin/node itself. Use the `--scripts-prepend-node-path` option to include the path for the node binary npm was executed with.
> gatsby-cli@2.12.46 typegen /Users/misiek/dev/gatsby/packages/gatsby-cli
> tsc --emitDeclarationOnly --declaration --declarationDir lib/
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/constants.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/index.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/redux/types.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/reporter-phantom.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/reporter-progress.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/reporter-timer.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/reporter.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/reporter/types.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/structured-errors/error-map.d.ts' because it would overwrite input file.
error TS5055: Cannot write file '/Users/misiek/dev/gatsby/packages/gatsby-cli/lib/structured-errors/types.d.ts' because it would overwrite input file.
Found 10 errors.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! gatsby-cli@2.12.46 typegen: `tsc --emitDeclarationOnly --declaration --declarationDir lib/`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the gatsby-cli@2.12.46 typegen script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/misiek/.npm/_logs/2020-06-17T09_42_11_646Z-debug.log
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Making sure we don't have declaration files before running typegen seems to fix (or rather work around this), so this is what this PR does

To reproduce the problem:

cd packages/gatsby-cli
yarn prepare
yarn prepare

2nd prepare will show those errors (1st one might too if you have those .d.ts files around already)

[blainekasten]

Yeah, this makes a ton of sense. We'll need to do this to gatsby-core-utils too probably

[ascorbic]

It aint pretty, but until we fix the imports this does the job