Use the latest Rust roll in 2e5c4436101c72e571732e77604be0bc8f38ee4c

The fallback gates the use of the roll, since autoroll script may
update Rust version but fail to build it still.

[email protected]

Bug: None
Change-Id: I610935656d01d3851311dbe87803e5926411a250
Cq-Include-Trybots: luci.chromium.try:android-rust-arm-dbg,android-rust-arm-rel,linux-rust-x64-dbg,linux-rust-x64-rel
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4261968
Reviewed-by: Collin Baker <[email protected]>
Commit-Queue: danakj <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1106487}
NOKEYCHECK=True
GitOrigin-RevId: 8f6ee5ed5468e3f3e071c38641115e7218101225

Author: danakj

update_rust.py

@@ -62,7 +62,7 @@
 # TODO(lukasza): Include CRUBIT_REVISION and CRUBIT_SUB_REVISION once we
 # include Crubit binaries in the generated package.  See also a TODO comment
 # in BuildCrubit in package_rust.py.
-FALLBACK_REVISION = '7919ef0ec5776c72dace7fec1c68551a617505ad-1-llvmorg-16-init-17653-g39da55e8-2'
+FALLBACK_REVISION = '6e0115778b0aedc90b59e035476c38e1b8c5c29b-1-llvmorg-17-init-2082-g6d4a674a-1'
 
 # Hash of src/stage0.json, which itself contains the stage0 toolchain hashes.
 # We trust the Rust build system checks, but to ensure it is not tampered with