Add a CI job for parallel rustc using x.py check

config.toml.example

@@ -268,6 +268,9 @@
 # Whether or not `panic!`s generate backtraces (RUST_BACKTRACE)
 #backtrace = true
 
+# Build rustc with experimental parallelization
+#experimental-parallel-queries = false
+
 # The default linker that will be hard-coded into the generated compiler for
 # targets that don't specify linker explicitly in their target specifications.
 # Note that this is not the linker used to link said compiler.

src/bootstrap/configure.py

@@ -44,6 +44,7 @@ def v(*args):
 o("docs", "build.docs", "build standard library documentation")
 o("compiler-docs", "build.compiler-docs", "build compiler documentation")
 o("optimize-tests", "rust.optimize-tests", "build tests with optimizations")
+o("experimental-parallel-queries", "rust.experimental-parallel-queries", "build rustc with experimental parallelization")
 o("test-miri", "rust.test-miri", "run miri's test suite")
 o("debuginfo-tests", "rust.debuginfo-tests", "build tests with debugger metadata")
 o("quiet-tests", "rust.quiet-tests", "enable quieter output when running tests")

src/ci/docker/x86_64-gnu-debug/Dockerfile

@@ -16,6 +16,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+ENV PARALLEL_CHECK 1
 ENV RUST_CONFIGURE_ARGS \
       --build=x86_64-unknown-linux-gnu \
       --enable-debug \

src/ci/run.sh

@@ -72,6 +72,13 @@ fi
 # sccache server at the start of the build, but no need to worry if this fails.
 SCCACHE_IDLE_TIMEOUT=10800 sccache --start-server || true
 
+if [ "$PARALLEL_CHECK" != "" ]; then
+  $SRC/configure --enable-experimental-parallel-queries
+  python2.7 ../x.py check
+  rm -f config.toml
+  rm -rf build
+fi
+
 travis_fold start configure
 travis_time_start
 $SRC/configure $RUST_CONFIGURE_ARGS