I've noticed that other people have been having problem with this build as well. I'm using amd64 Current, (8.99.23). The build get part way through and them I see these errors:
...
[0m [0m [1m [32m Compiling [0m mozurl v0.0.1 (/usr/pkgsrc/www/firefox/work/firefox-65.0/netwerk/base/mozurl)
[0m [0m [1m [32m Compiling [0m malloc_size_of v0.0.1 (/usr/pkgsrc/www/firefox/work/firefox-65.0/servo/components/malloc_size_of)
[0m [0m [1m [32m Compiling [0m style v0.0.1 (/usr/pkgsrc/www/firefox/work/firefox-65.0/servo/components/style)
[0m [0m [1m [32m Compiling [0m style_traits v0.0.1 (/usr/pkgsrc/www/firefox/work/firefox-65.0/servo/components/style_traits)
[0m [0m [1m [31merror: [0m failed to run custom build command for `style v0.0.1 (/usr/pkgsrc/www/firefox/work/firefox-65.0/servo/components/style)`
process didn't exit successfully: `/usr/pkgsrc/www/firefox/work/build/release/build/style-befeb61317869ca7/build-script-build` (exit code: 101)
--- stdout
cargo:out_dir=/usr/pkgsrc/www/firefox/work/build/x86_64-unknown-netbsd/release/build/style-751c2d4c017ded8e/out
c
....
There are more backtraces and such from clang, but I don't know if it's very useful. I'm wondering if this is a resource issue. Before, I would get "resource exhausted" from my /tmp directory, even though there was 64M of space. I increased this to 256M with tmpfs, and then things run ok, until now. The "Compiling malloc_size_of v0.0.1" looks suspicious. Any thoughs?