The theory
In your settings, the bash command associated with BibTeX is: bibtex build/%. It means: "look for the (implicitely said .aux) file in following folder: <location of the .tex file you're compiling>/build".
This is handy when you tell (pdf)LaTeX to put every temporary/auxiliary files in a subfolder (here name build) in order to keep the original folder "clean". You activate this behavior using the -output-directory option while running (pdf)LaTeX (e.g., pdflatex -output-directory=build/ %.tex).
Your case
However, since you did not enabled this feature (i.e., the bash command used for (pdf)LaTeX compiling does not call the -output-directory option), all temp files are created in the same folder than the .tex file you are compiling.
But in your case, bibtex is still looking for the .aux-file in a non-existing subfolder named build: bibtex build/%.
The solution
Thus, you should tell bibtex to look for the .aux file in the same folder than your .tex file, i.e. write bibtex % instead of bibtex build/% at the BibTeX line.
(Or you could also create a subfolder named build, and use following commands: pdfLaTeX: pdflatex -output-directory=build/ %.tex; bibTeX: bibtex build/%. But you would also need to update paths for other commands (e.g. pdf-viewer).)
bibtex %instead ofbibtex build/%. – ebosi Oct 19 '16 at 07:46(-;! Have a look here. I suggest you to take some time to browse some introduction to LaTeX (e.g. the (not) so short one): it's worth the time/effort invested in it! – ebosi Oct 19 '16 at 08:18