info!/error! cut off strings that are too long

[jdm]

Case in point, running RUST_LOG=rustc::back::link while building servo shows me

rust: ~"cc link args: -L/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib -m64 -o servo servo.o -L/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib -lcore-c3ca5d77d81b46c1-0.6 -L/usr/local/lib/rustc/x86_64-unknown-linux-gnu/lib -lstd-4782a756585a81-0.6 -L/home/jdm/sdb/servo/build/src/rust-geom -lgeom-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-xlib -lxlib-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-freetype -lfreetype-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-fontconfig -lfontconfig-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-cairo -lcairo-24298d4e74ef213e-0.1 -L/home/jdm/sdb/servo/build/src/rust-azure -lazure-91b694222f4eaba-0.1 -L/home/jdm/sdb/servo/build/src/rust-http-client -lhttp_client-5d54f435f73e8b66-0.1 -L/home/jdm/sdb/servo/build/src/rust-stb-image -lstb_image-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-harfbuzz -lharfbuzz-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/servo-gfx -lservo_gfx-60c1172840c97add-0.1 -L/home/jdm/sdb/servo/build/src/rust-glut -lglut-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-hubbub -lhubbub-68a2c114141ca-0.1 -L/home/jdm/sdb/servo/build/src/rust-mozjs -ljs-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-opengles -lopengles-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-layers -llayers-2d4fceb1d85c78b5-0.1 -L/home/jdm/sdb/servo/build/src/rust-wapcaplet -lwapcaplet-94839cbfe144198-0.1 -L/home/jdm/sdb/servo/build/src/rust-netsurfcss -lnetsurfcss-ecae1ab066319bc9-0.1 -L/home/jdm/sdb/servo/build/src/rust-css -lcss-9dfe8711fa4294-0.1 -L/home/jdm/sdb/servo/build/src/sharegl -lsharegl-7336e7557906993-0.1 -L/home/jdm/sdb/servo/build/src/rust-freetype -L/home/jdm/sdb/servo/build/src/rust-fontconfig -L/home/jdm/sdb/servo/build/src/rust-xlib -L/home/jdm/sdb/servo/build/src/libwapcaplet -L/home/jdm/sdb/servo/build/src/rust-wapcaplet -L/home/jdm/sdb/servo/build/src/rust-harfbuzz -L/home/jdm/sdb/servo/build/src/rust-opengles -L/home/jdm/sdb/servo/build/src/skia -L/home/jdm/sdb/servo/build/[...]

This is less than ideal.

[catamorphism]

Doesn't seem critical for 0.7. Nominating for milestone 5 (production ready).

[graydon]

subtask of #3309 really; this is working as intended