Set MAX_JOBS to nproc - 1 if using sccache to compile CUDA (#7361)

* Set MAX_JOBS to nproc - 1 if using sccache to compile CUDA

* Change JOBS setting in tools/cpp_build/build_common.sh

.jenkins/pytorch/build.sh

@@ -27,6 +27,11 @@ if ! which conda; then
   pip install mkl mkl-devel
 fi
 
+# sccache will fail for CUDA builds if all cores are used for compiling
+if [[ "$BUILD_ENVIRONMENT" == *cuda* ]] && which sccache > /dev/null; then
+  export MAX_JOBS=`expr $(nproc) - 1`
+fi
+
 WERROR=1 python setup.py install
 
 # Add the ATen test binaries so that they won't be git clean'ed away

tools/cpp_build/build_common.sh

@@ -27,7 +27,9 @@ BUILD_TYPE=${BUILD_TYPE:-Debug}
 # Try to build with as many threads as we have cores, default to 4 if the
 # command fails.
 set +e
-if [[ "$(uname)" == "Linux" ]]; then
+if [ -n "$MAX_JOBS" ]; then  # Use MAX_JOBS if it is set
+  JOBS=$MAX_JOBS
+elif [[ "$(uname)" == "Linux" ]]; then
   # https://stackoverflow.com/questions/6481005/how-to-obtain-the-number-of-cpus-cores-in-linux-from-the-command-line
   JOBS="$(grep -c '^processor' /proc/cpuinfo)"
 else # if [[ "$(uname)" == "Darwin"]]