I want to get Servo vendored into servo/. The previous plan was to
replace the dummy geckolib with the real deal when the vendoring is
done. Unfortunately, this will require a significant `cargo vendor`
change, which we want to punt on for a bit.
So, this commit moves our dummy geckolib outside of servo/ so we
don't need to `cargo update` or `cargo vendor` when the real servo/
is installed.
The change to toolkit/library/rust/shared/Cargo.toml can be reverted
in the stylo repo to allow it to use the real geckolib.
We also update the taskgraph code for detecting Servo. Previously,
it looked for a file in the possibly-vendored servo/ directory. Once
the vendoring happens, this check will always pass. But without the
real geckolib, the Servo builds will fail. So, we change the check
to look for the real geckolib. This is implemented a bit hackily.
But it will be short-lived until we run `cargo vendor`.
MozReview-Commit-ID: CxGTwy6bK9j
In our current Rust world, we have the following dependency structure:
xul.so --------------------------+
|
xul-gtest.so -+--> xul.a --------+-> gkrust
|
+--> gkrust-gtest
This structure results in link errors with multiply-defined symbols
between gkrust-gtest and gkrust with newer Rust releases when linking
xul-gtest.so. So we have to do something different.
Our new structure is:
xul.so --------------------------+
|
xul-gtest.so -+--> xul.a --------+-> gkrust --+-> gkrust-shared
| |
+--> gkrust-gtest --------------+
and we enforce that a given shared library can only have at most one
Rust library that it depends on. Said Rust library is assumed to
include all significant Rust dependencies of the dependent static
libraries as well. (In the above structure, gkrust is simply a wrapper
around gkrust-shared, so gkrust-gtest doesn't have to include gkrust as
a dependency.)
