Bug 1326486 - build-clang: Add support for 4-stage builds r=glandium

Separating out the mechanical/"boring" changes to make the next patch more clear. This patch adds the ability to build a fourth stage that for now doesn't do anything special.

I changed to using >= to make it more obvious that e.g. "here is what's going to happen for stage 2" -- the off-by-one was too hard on my brain.

Differential Revision: https://phabricator.services.mozilla.com/D69079

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

build/build-clang/README

@@ -28,7 +28,7 @@ Config file format
 
 build-clang.py accepts a JSON config format with the following fields:
 
-* stages: Use 1, 2, or 3 to select different compiler stages.  The default is 3.
+* stages: Use 1, 2, 3 or 4 to select different compiler stages.  The default is 3.
 * python_path: Path to the Python 2.7 installation on the machine building clang.
 * gcc_dir: Path to the gcc toolchain installation, only required on Linux.
 * cc: Path to the bootsraping C Compiler.

build/build-clang/build-clang.py

@@ -597,8 +597,8 @@ if __name__ == "__main__":
     stages = 3
     if "stages" in config:
         stages = int(config["stages"])
-        if stages not in (1, 2, 3):
-            raise ValueError("We only know how to build 1, 2, or 3 stages")
+        if stages not in (1, 2, 3, 4):
+            raise ValueError("We only know how to build 1, 2, 3, or 4 stages.")
     build_type = "Release"
     if "build_type" in config:
         build_type = config["build_type"]
@@ -790,7 +790,7 @@ if __name__ == "__main__":
 
     runtimes_source_link = llvm_source_dir + "/runtimes/compiler-rt"
 
-    if stages > 1:
+    if stages >= 2:
         stage2_dir = build_dir + '/stage2'
         stage2_inst_dir = stage2_dir + '/' + package_name
         final_stage_dir = stage2_dir
@@ -810,7 +810,7 @@ if __name__ == "__main__":
             is_final_stage=(stages == 2), android_targets=android_targets,
             extra_targets=extra_targets)
 
-    if stages > 2:
+    if stages >= 3:
         stage3_dir = build_dir + '/stage3'
         stage3_inst_dir = stage3_dir + '/' + package_name
         final_stage_dir = stage3_dir
@@ -829,6 +829,25 @@ if __name__ == "__main__":
             compiler_rt_source_dir, runtimes_source_link, compiler_rt_source_link,
             (stages == 3), extra_targets=extra_targets)
 
+    if stages >= 4:
+        stage4_dir = build_dir + '/stage4'
+        stage4_inst_dir = stage4_dir + '/' + package_name
+        final_stage_dir = stage4_dir
+        final_inst_dir = stage4_inst_dir
+        build_one_stage(
+            [stage3_inst_dir + "/bin/%s%s" %
+                (cc_name, exe_ext)] + extra_cflags2,
+            [stage3_inst_dir + "/bin/%s%s" %
+                (cxx_name, exe_ext)] + extra_cxxflags2,
+            [stage3_inst_dir + "/bin/%s%s" %
+                (cc_name, exe_ext)] + extra_asmflags,
+            [ld] + extra_ldflags,
+            ar, ranlib, libtool,
+            llvm_source_dir, stage4_dir, package_name, build_libcxx, osx_cross_compile,
+            build_type, assertions, python_path, gcc_dir, libcxx_include_dir, build_wasm,
+            compiler_rt_source_dir, runtimes_source_link, compiler_rt_source_link,
+            (stages == 4), extra_targets=extra_targets)
+
     if build_clang_tidy:
         prune_final_dir_for_clang_tidy(os.path.join(final_stage_dir, package_name),
                                        osx_cross_compile)