Instead of assuming there is an HTML file for each diagnostics, consider
the HTML files only when they exist, individually of each other.
After generating the reference data, running
python /scripts/SATest.py build --projects simbody
was resulting in this error:
File "/scripts/CmpRuns.py", line 250, in read_single_file
assert len(d['HTMLDiagnostics_files']) == 1
KeyError: 'HTMLDiagnostics_files'
Reviewed By: steakhal
Differential Revision: https://reviews.llvm.org/D126197