rustbuild: Add sccache support

This commit adds support for sccache, a ccache-like compiler which works on MSVC
and stores results into an S3 bucket. This also switches over all Travis and
AppVeyor automation to using sccache to ensure a shared and unified cache over
time which can be shared across builders.

The support for sccache manifests as a new `--enable-sccache` option which
instructs us to configure LLVM differently to use a 'sccache' binary instead of
a 'ccache' binary. All docker images for Travis builds are updated to download
Mozilla's tooltool builds of sccache onto various containers and systems.
Additionally a new `rust-lang-ci-sccache` bucket is configured to hold all of
our ccache goodies.

1 files changed, 17 insertions, 4 deletions

diff --git a/configure b/configure
index 0a07e41fb97..e495c0d3abd 100755
--- a/configure
+++ b/configure
@@ -621,6 +621,7 @@ opt llvm-assertions 0 "build LLVM with assertions"
 opt debug-assertions 0 "build with debugging assertions"
 opt fast-make 0 "use .gitmodules as timestamp for submodule deps"
 opt ccache 0 "invoke gcc/clang via ccache to reuse object files between builds"
+opt sccache 0 "invoke gcc/clang via sccache to reuse object files between builds"
 opt local-rust 0 "use an installed rustc rather than downloading a snapshot"
 opt local-rebuild 0 "assume local-rust matches the current version, for rebuilds; implies local-rust, and is implied if local-rust already matches the current version"
 opt llvm-static-stdcpp 0 "statically link to libstdc++ for LLVM"
@@ -1677,11 +1678,23 @@ do
             LLVM_CC_64_ARG1="gcc"
             ;;
         ("gcc")
-            LLVM_CXX_32="g++"
-            LLVM_CC_32="gcc"
+            if [ -z "$CFG_ENABLE_SCCACHE" ]; then
+                LLVM_CXX_32="g++"
+                LLVM_CC_32="gcc"
 
-            LLVM_CXX_64="g++"
-            LLVM_CC_64="gcc"
+                LLVM_CXX_64="g++"
+                LLVM_CC_64="gcc"
+            else
+                LLVM_CXX_32="sccache"
+                LLVM_CC_32="sccache"
+                LLVM_CXX_32_ARG1="g++"
+                LLVM_CC_32_ARG1="gcc"
+
+                LLVM_CXX_64="sccache"
+                LLVM_CC_64="sccache"
+                LLVM_CXX_64_ARG1="g++"
+                LLVM_CC_64_ARG1="gcc"
+            fi
             ;;
 
         (*)