I recently bisected my mozconfig after I realized that my builds were appreciably slower than I expected; I discovered that the main reason for this is the clang-plugin, which caused approximately a 50% slowdown in my local build time:

## No Clang Plugin 
$  ./mach clobber && time ./mach build 
real    9m9.583s
user    201m22.020s
sys     11m16.940s

## Yes Clang Plugin (ac_add_options --enable-clang-plugin)
$ ./mach clobber && time ./mach build 
real    15m21.131s
user    366m14.555s
sys     13m44.436s

This has eaten a large amount of my build time over the past while; it would be nice if running the clang plugin didn't cause builds to slow down by 50%.

This is a very broad statement because each checker chips a little bit from the performance and in the end why don't you use ./mach static-analysis check <file>?

Mostly because I had no idea mach static-analysis check was a thing; perhaps it should be warning in regular developer builds that --enable-clang-plugin builds probably aren't what regular developers ought to use.