gatsby: SSL errors when using `gatsby develop --https`

Description

When running gatsby develop --https both with without --cert-file/--key-file SSL does not work in Firefox, Chrome or Safari (screenshots below).

Steps to reproduce

1. I’ve created a minimal reproduction in https://github.com/patrickarlt/gatsby-ssl-issue-reproduction. This is based off the default starter with the latest version of Gatsby.
2. npm install
3. npm run start:devcert this starts the local dev server and automatically creates SSL certs.
4. Observe failures.
5. Install mkcert, for Mac this means:
   • brew install mkcert
   • brew install nss
   • mkcert install
   • mkcert localhost
6. npm run start:local-certs this starts the dev server with the local certs from mkcert
7. Observe failures.

In order to check that the certs are valid you can use http-server:

• npm i -g http-server
• http-server . -C localhost.pem -K localhost-key.pem -S -a localhost

This displays the directory structure of our project tin the browser over https://... note the lock icon in Chrome:

Expected result

The server should successfully serve pages over https://....

Actual result

Browsers produce SSL errors.

Environment

Gatsby

  System:
    OS: macOS Mojave 10.14.6
    CPU: (8) x64 Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz
    Shell: 5.3 - /bin/zsh
  Binaries:
    Node: 14.3.0 - ~/.nvm/versions/node/v14.3.0/bin/node
    npm: 6.14.5 - ~/.nvm/versions/node/v14.3.0/bin/npm
  Languages:
    Python: 2.7.10 - /usr/bin/python
  Browsers:
    Chrome: 81.0.4044.138
    Firefox: 77.0
    Safari: 13.1
  npmPackages:
    gatsby: ^2.22.3 => 2.22.3

OpenSSL

$ openssl version
LibreSSL 2.6.5

mkcert

$ brew info mkcert 
mkcert: stable 1.4.1 (bottled)
Simple tool to make locally trusted development certificates
https://github.com/FiloSottile/mkcert
/usr/local/Cellar/mkcert/1.4.1 (6 files, 5.3MB) *
  Poured from bottle on 2020-04-08 at 18:45:14
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/mkcert.rb
==> Dependencies
Build: go ✘
==> Analytics
install: 3,827 (30 days), 11,641 (90 days), 47,679 (365 days)
install-on-request: 3,351 (30 days), 10,186 (90 days), 40,390 (365 days)
build-error: 0 (30 days)

nss

$ brew info nss
nss: stable 3.52 (bottled)
Libraries for security-enabled client and server applications
https://developer.mozilla.org/docs/NSS
/usr/local/Cellar/nss/3.52 (225 files, 34.1MB) *
  Poured from bottle on 2020-05-19 at 16:52:58
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/nss.rb
==> Dependencies
Required: nspr ✔
==> Analytics
install: 38,963 (30 days), 105,774 (90 days), 394,028 (365 days)
install-on-request: 8,110 (30 days), 19,022 (90 days), 62,334 (365 days)
build-error: 0 (30 days)