Use a tmpfs build directory

Author: resistor

.cirrus.yml

@@ -20,6 +20,7 @@ pr_task:
     - apt-get install -y clang ninja-build lld cmake ccache perl
   configure_script:
     - mkdir Build
+    - mount -t tmpfs -o size=20G tmpfs Build
     - cd Build
     - cmake ../llvm -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;lld" -DLLVM_ENABLE_UNWIND_TABLES=NO -DLLVM_ENABLE_LLD=ON -DLLVM_PARALLEL_LINK_JOBS=1 -DLLVM_APPEND_VC_REV=ON -DLLVM_VC_REPOSITORY=${CIRRUS_REPO_FULL_NAME} -DLLVM_FORCE_VC_REPOSITORY=${CIRRUS_REPO_FULL_NAME}-DLLVM_VC_REVISION=${CIRRUS_CHANGE_IN_REPO} -DLLVM_CCACHE_BUILD=ON -G Ninja
   build_script: