diagram-generator: hide pdflatex output

Output of pdflatex (which is called during conversion of TikZ images) is
mostlly noise and will only be shown if PDF creation fails.

Author: tarleb

diagram-generator/diagram-generator.lua

@@ -115,7 +115,7 @@ local function tikz2image(src, filetype, additionalPackages)
     f:close()
 
     -- Execute the LaTeX compiler:
-    os.execute(pdflatexPath .. " -output-directory " .. tmpDir .. " " .. tmp)
+    pandoc.pipe(pdflatexPath, {'-output-directory', tmpDir, tmp}, '')
 
     -- Build the basic Inkscape command for the conversion:
     local baseCommand = " --without-gui --file=" .. tmp .. ".pdf"