With Ninja, the build is unnecessarily noisy:
[21/81] Generating plugin.c
Generated plugin.c for l16_mono.
[22/81] Generating plugin.c
Generated plugin.c for G711.
Avoid writing `Generated plugin.c for G711` and generate a single line
such as `Generating plugins/codecs/G711/plugin.c` instead.
Do not write the absolute path to plugin.c, this should hopefully help
with reproducible builds that are independent of the build directory.