Bug 1690934 - Adjust clang for use with sysroots. r=firefox-build-system-reviewers,sheehan,mhentges

When using the --sysroot argument to clang, clang changes where it
searches for libraries in its own directory, and excludes the lib and
lib32 subdirectories. So we need to move the gcc files to a place where
it does look (and that it also looks without --sysroot).

We however still keep a copy of libstdc++ in the lib directory for
runtime purposes.

Differential Revision: https://phabricator.services.mozilla.com/D104123

build/build-clang/build-clang.py

@@ -21,6 +21,7 @@ import sys
 import tarfile
 from contextlib import contextmanager
 from distutils.dir_util import copy_tree
+from distutils.file_util import copy_file
 
 from shutil import which
 
@@ -196,10 +197,13 @@ def install_libgcc(gcc_dir, clang_dir, is_final_stage):
     mkdir_p(clang_lib_dir)
     copy_tree(libgcc_dir, clang_lib_dir, preserve_symlinks=True)
     libgcc_dir = os.path.join(gcc_dir, "lib64")
-    clang_lib_dir = os.path.join(clang_dir, "lib")
+    # This is necessary as long as CI runs on debian8 docker images.
+    copy_file(
+        os.path.join(libgcc_dir, "libstdc++.so.6"), os.path.join(clang_dir, "lib")
+    )
     copy_tree(libgcc_dir, clang_lib_dir, preserve_symlinks=True)
     libgcc_dir = os.path.join(gcc_dir, "lib32")
-    clang_lib_dir = os.path.join(clang_dir, "lib32")
+    clang_lib_dir = os.path.join(clang_lib_dir, "32")
     copy_tree(libgcc_dir, clang_lib_dir, preserve_symlinks=True)
     include_dir = os.path.join(gcc_dir, "include")
     clang_include_dir = os.path.join(clang_dir, "include")