message: (Fix James-Yu#1528) Launch pdftex with child_process.exec
  MiKTeX's pdftex has issues launching with child_process.spawn for whatever reason.
diff: @@ -321,20 +321,7 @@ export class TikzPictureView {
  private precompilePreamble(file: string, preamble: string) {
  return new Promise((resolve, reject) => {
  fs.writeFileSync(file, `\\documentclass{standalone}\n\n${preamble}\n\n\\begin{document}\\end{document}`)
  - const process = child_process.spawn(
  - 'pdftex',
  - [
  - '-ini',
  - '-interaction=nonstopmode',
  - '-shell-escape',
  - '-file-line-error',
  - '-jobname="preamble"',
  - '"&pdflatex"',
  - 'mylatexformat.ltx',
  - `"${file}"`
  - ],
  - { cwd: path.dirname(file) }
  - )
  + const process = child_process.exec( `pdftex -ini -interaction=nonstopmode -shell-escape -file-line-error -jobname="preamble" "&pdflatex" mylatexformat.ltx ${path.basename(file)}`, { cwd: path.dirname(file) } )
  process.on('exit', _code => {
  resolve()
  })
  