Copy LLVM build artifacts to output dir when compilation fails

This CL causes the build system to copy LLVM build artifacts to the
output dist directory if the invocation of `x.py` fails.

Test: None
Change-Id: I3da9a55b253af541e80c58c224beb64757e456bb

Author: chriswailes

do_build.py

@@ -51,6 +51,19 @@
         "vendor/unicode-width",
 ]
 
+LLVM_BUILD_PATHS_OF_INTEREST: list[str] = [
+    'build.ninja',
+    'cmake',
+    'CMakeCache.txt',
+    'CMakeFiles',
+    'cmake_install.cmake',
+    'compile_commands.json',
+    'CPackConfig.cmake',
+    'CPackSourceConfig.cmake',
+    'install_manifest.txt',
+    'llvm.spec'
+]
+
 
 def parse_args():
     """Parses arguments and returns the parsed structure."""
@@ -149,6 +162,9 @@ def main():
                           '--stage', '3', 'install'], cwd=OUT_PATH_RUST_SOURCE, env=env).wait()
     if ec != 0:
         print("Build stage failed with error {}".format(ec))
+        tarball_path = dist_dir / 'llvm-build-config.tar.gz'
+        subprocess.check_call(['tar', 'czf', tarball_path] + LLVM_BUILD_PATHS_OF_INTEREST,
+            cwd=LLVM_BUILD_PATH)
         sys.exit(ec)
 
     # Install sources

paths.py

@@ -33,6 +33,8 @@
 OUT_PATH_STDLIB_SRCS: Path = OUT_PATH_PACKAGE / 'src' / 'stdlibs'
 OUT_PATH_WRAPPERS:    Path = OUT_PATH / 'wrappers'
 
+LLVM_BUILD_PATH: Path = OUT_PATH_RUST_SOURCE / 'build' / 'x86_64-unknown-linux-gnu' / 'llvm' / 'build'
+
 PREBUILT_PATH:         Path = WORKSPACE_PATH / 'prebuilts'
 RUST_PREBUILT_PATH:    Path = PREBUILT_PATH / 'rust' / build_platform.prebuilt() / STAGE0_RUST_VERSION
 LLVM_PREBUILT_PATH:    Path = PREBUILT_PATH / 'clang' / 'host' / build_platform.prebuilt() / CLANG_NAME