||LD_PRELOAD library that intercepts some libc functions and lowercases
paths under a given set of directories before calling the real libc
The set of directories is defined with the LOWERCASE_DIRS environment
variable, separated with a `:`.
Only the parts of the directories below the LOWERCASE_DIRS directories
For example, with LOWERCASE_DIRS=/Foo:/Bar:
`/home/QuX` is unchanged.
`/Foo/QuX` becomes `/Foo/qux`.
`/foo/QuX` is unchanged.
`/Bar/QuX` becomes `/Bar/qux`.
This is, by no means, supposed to be a generic LD_PRELOAD library. It
only intercepts the libc functions that matter in order to build Firefox.