Bug 1451104 - part 3 - inform stage2/3 clang about gcc binutils; r=glandium

We do this to encourage clang to find an new-enough linker instead of
the system one.

Differential Revision: https://phabricator.services.mozilla.com/D22881

--HG--
extra : moz-landing-system : lando

build/build-clang/build-clang.py

@@ -120,8 +120,23 @@ def delete(path):
             pass
 
 
-def install_libgcc(gcc_dir, clang_dir):
-    out = subprocess.check_output([os.path.join(gcc_dir, "bin", "gcc"),
+def install_libgcc(gcc_dir, clang_dir, is_final_stage):
+    gcc_bin_dir = os.path.join(gcc_dir, 'bin')
+
+    # Copy over gcc toolchain bits that clang looks for, to ensure that
+    # clang is using a consistent version of ld, since the system ld may
+    # be incompatible with the output clang produces.  But copy it to a
+    # target-specific directory so a cross-compiler to Mac doesn't pick
+    # up the (Linux-specific) ld with disastrous results.
+    #
+    # Only install this for the bootstrap process; we expect any consumers of
+    # the newly-built toolchain to provide an appropriate ld themselves.
+    if not is_final_stage:
+        x64_bin_dir = os.path.join(clang_dir, 'x86_64-unknown-linux-gnu', 'bin')
+        mkdir_p(x64_bin_dir)
+        shutil.copy2(os.path.join(gcc_bin_dir, 'ld'), x64_bin_dir)
+
+    out = subprocess.check_output([os.path.join(gcc_bin_dir, "gcc"),
                                    '-print-libgcc-file-name'])
 
     libgcc_dir = os.path.dirname(out.rstrip())
@@ -309,7 +324,7 @@ def build_one_stage(cc, cxx, asm, ld, ar, ranlib, libtool,
     build_package(build_dir, cmake_args)
 
     if is_linux():
-        install_libgcc(gcc_dir, inst_dir)
+        install_libgcc(gcc_dir, inst_dir, is_final_stage)
     # For some reasons the import library clang.lib of clang.exe is not
     # installed, so we copy it by ourselves.
     if is_windows():
@@ -405,7 +420,9 @@ def get_tool(config, key):
 #       run-clang-tidy.py
 def prune_final_dir_for_clang_tidy(final_dir, osx_cross_compile):
     # Make sure we only have what we expect.
-    dirs = ("bin", "include", "lib", "lib32", "libexec", "msbuild-bin", "share", "tools")
+    dirs = ["bin", "include", "lib", "lib32", "libexec", "msbuild-bin", "share", "tools"]
+    if is_linux():
+        dirs.append("x86_64-unknown-linux-gnu")
     for f in glob.glob("%s/*" % final_dir):
         if os.path.basename(f) not in dirs:
             raise Exception("Found unknown file %s in the final directory" % f)
@@ -422,6 +439,10 @@ def prune_final_dir_for_clang_tidy(final_dir, osx_cross_compile):
 
     # Keep include/ intact.
 
+    # Remove the target-specific files.
+    if is_linux():
+        shutil.rmtree(os.path.join(final_dir, "x86_64-unknown-linux-gnu"))
+
     # In lib/, only keep lib/clang/N.M.O/include and the LLVM shared library.
     re_ver_num = re.compile(r"^\d+\.\d+\.\d+$", re.I)
     for f in glob.glob("%s/lib/*" % final_dir):