Replace Istanbul with nyc, Istanbul's CLI. nyc appears to have some
bugs that this patch works around:
- When all files in the project are considered, not just those
imported via tests, the coverage rates and line numbers vary between
runs. This patch disables the `all` option for now and points to the
bug:
https://github.com/istanbuljs/nyc/issues/537#issuecomment-390814662.
- Source map line numbers appear to be incorrect except when `all` is
enabled and working correctly (see previous bullet).
- `sourceMap` must be disabled to avoid ENAMETOOLONG errors when nyc
tries to include them as encoded strings. The patch disables the
setting and points to: https://github.com/istanbuljs/nyc/issues/847.
Using babel-plugin-istanbul and source-map-support appears to have
no effect (the former in tests/node-qunit/run.js and .babelrc).
- CI fails with
`Error: EACCES: permission denied, mkdir '/nonexistent'`. Specify
`SPAWN_WRAP_SHIM_ROOT` instead of constructing a subdirectory from a
nonexistent home directory.
Bug: T196952
Bug: T193519
Change-Id: Idf2e3accd4a6277cbef91c1156fcd206c9e7d882
