asymptote: builds hanging for some macOS releases, causing them to be auto-killed by buildbots

[mascguy (Christopher Nielsen)]

During the build process, this port appears to sometimes hang, causing the jobs to ultimately be killed by buildbot. (And tying up the buildbots for a full hour, before being ultimately terminated.)

Attached is an example build for 10.8, though the pattern appears to be the same across versions/architectures:

[...]

Package media9 Warning: Rerun to get internal references right!

[1{/opt/local/var/db/texmf/fonts/map/pdftex/updmap/pdftex.map} <./latexusage-1_
0.pdf> <./latexusage-2+0_0.pdf> <./latexusage-3_0.pdf>] (./latexusage.aux)

LaTeX Font Warning: Size substitutions with differences
(Font)              up to 0.88pt have occurred.

 )</opt/local/share/texmf-texlive/fonts/type1/public/amsfonts/cm/cmmi12.pfb></o
pt/local/share/texmf-texlive/fonts/type1/public/amsfonts/cm/cmmib10.pfb></opt/l
ocal/share/texmf-texlive/fonts/type1/public/amsfonts/cm/cmr12.pfb></opt/local/s
hare/texmf-texlive/fonts/type1/public/amsfonts/cm/cmr17.pfb></opt/local/share/t
exmf-texlive/fonts/type1/public/amsfonts/cm/cmr8.pfb></opt/local/share/texmf-te
xlive/fonts/type1/public/amsfonts/cm/cmsy10.pfb></opt/local/share/texmf-texlive
/fonts/type1/public/amsfonts/cm/cmtt12.pfb>
Output written on latexusage.pdf (1 page, 88491 bytes).
Transcript written on latexusage.log.

command timed out: 3600 seconds without output running ['./mpbb/mpbb', '--prefix', '/opt/local', 'install-port', 'asymptote'], attempting to kill