Backed out 3 changesets (bug 1863497) for causing bustages. CLOSED TREE

Backed out changeset ce9934edcec1 (bug 1863497)
Backed out changeset c959dafcf46f (bug 1863497)
Backed out changeset 1caa79ee637e (bug 1863497)

Makefile.in

@@ -147,9 +147,9 @@ include $(topsrcdir)/config/rules.mk
 
 ifdef SCCACHE_VERBOSE_STATS
 default::
-	-$(CCACHE) --show-adv-stats --stats-format=json > '$(UPLOAD_PATH)/sccache-stats.json'
+	-$(CCACHE) --show-stats --stats-format=json > '$(UPLOAD_PATH)/sccache-stats.json'
 	@echo "===SCCACHE STATS==="
-	-$(CCACHE) --show-adv-stats
+	-$(CCACHE) --show-stats
 	@echo "==================="
 endif
 

build/docs/sccache-dist.rst

@@ -5,12 +5,7 @@ Distributed sccache (sccache-dist)
 ==================================
 
 `sccache <https://github.com/mozilla/sccache>`_ is a ccache-like tool written in
-Rust by Mozilla and many contributors.
-
-sccache-dist, its distributed variant, elevates this functionality by enabling
-the distribution and caching of Rust compilations across multiple machines.
-Please consider using sccache-dist when you have several machines
-compiling Firefox on the same network.
+Rust by Mozilla.
 
 The steps for setting up your machine as an sccache-dist server are detailed below.
 

docs/contributing/contribution_quickref.rst

@@ -97,12 +97,6 @@ Once the System is bootstrapped, run:
 which will check for dependencies and start the build.
 This will take a while; a few minutes to a few hours depending on your hardware.
 
-.. note::
-
-    If you build Firefox often, add `ac_add_options --with-ccache=sccache` to .mozconfig.
-    sccache will significantly speed up your builds by caching compilation results.
-    The Firefox build system will download sccache automatically.
-
 .. note::
 
     The default build is a compiled build with optimizations. Check out the

docs/setup/configuring_build_options.rst

@@ -219,13 +219,6 @@ supports `distributed compilation
 In order to enable ``sccache`` for Firefox builds, you can use
 ``ac_add_options --with-ccache=sccache``.
 
-From version 0.7.2, sccache local builds are using the ``preprocessor cache mode``
-by default. With a hot cache, it decreases the build time by a factor of 2 to 3
-compared the previous method. This feature works like the `direct mode in ccache
-<https://ccache.dev/manual/3.7.9.html#_the_direct_mode>`__,
-using a similar way to handle caching and dependencies.
-
-
 Optimization
 ^^^^^^^^^^^^
 

taskcluster/ci/fetch/toolchains.yml

@@ -297,8 +297,8 @@ sccache:
     fetch:
         type: git
         repo: https://github.com/mozilla/sccache
-        # 0.7.2 release
-        revision: f6fd5ddd2ad8370cada6b106fb254de099f96da5
+        # 0.5.4 release + a few patches
+        revision: a21e9f89e161d38cb078fcdb42cdcff1d7c0356b
 
 fxc2:
     description: fxc2 source code