From 30b268dd7d8da498c15907470bc5d7b642664317 Mon Sep 17 00:00:00 2001
From: Bert Belder <bertbelder@gmail.com>
Date: Fri, 7 Sep 2018 20:19:44 +0200
Subject: [PATCH] build: override host_toolchain on windows to use sccache with
 v8

---
 build_extra/toolchain/validate.gni | 22 +++++++++++++---------
 tools/setup.py                     | 11 ++++++-----
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/build_extra/toolchain/validate.gni b/build_extra/toolchain/validate.gni
index 79c013e8df..a1fe7189bf 100644
--- a/build_extra/toolchain/validate.gni
+++ b/build_extra/toolchain/validate.gni
@@ -2,14 +2,18 @@
 
 import("//build/toolchain/cc_wrapper.gni")
 
-# Verify that cc_wrapper is correctly set up on Windows.
-if (is_win && cc_wrapper != "" && custom_toolchain == "") {
-  suggested_toolchain = "//build_extra/toolchain/win:win_clang_$target_cpu"
+# Verify that the cc_wrapper/toolchain combo correctly set up on Windows.
+if (is_win && cc_wrapper != "") {
+  cc_wrapper_toolchain = "//build_extra/toolchain/win:win_clang_$target_cpu"
+  toolchain_supports_cc_wrapper = cc_wrapper_toolchain == default_toolchain &&
+                                  cc_wrapper_toolchain == host_toolchain
 
-  # Use print instead of assert with message for readability.
-  print(
-      "The 'cc_wrapper' option isn't supported by the default Windows toolchain.")
-  print("To make it work, add the option:")
-  print("  custom_toolchain=\"$suggested_toolchain\"")
-  assert(custom_toolchain != "")
+  if (!toolchain_supports_cc_wrapper) {
+    # Using print instead of assert-with-message for readability of the output.
+    print("The 'cc_wrapper' option isn't supported by the default Windows" +
+          " toolchain. To make it work, add these gn arguments:")
+    print("  custom_toolchain=\"$cc_wrapper_toolchain\"")
+    print("  host_toolchain=\"$cc_wrapper_toolchain\"")
+    assert(toolchain_supports_cc_wrapper)
+  }
 }
diff --git a/tools/setup.py b/tools/setup.py
index 9dff9eb207..737f80017f 100755
--- a/tools/setup.py
+++ b/tools/setup.py
@@ -59,12 +59,13 @@ def get_gn_args():
     # Check if ccache or sccache are in the path, and if so we set cc_wrapper.
     cc_wrapper = find_executable("ccache") or find_executable("sccache")
     if cc_wrapper:
-        out += [r'cc_wrapper="%s"' % cc_wrapper]
-        # Windows needs a custom toolchain for cc_wrapper to work.
+        out += ['cc_wrapper="%s"' % cc_wrapper]
+        # For cc_wrapper to work on Windows, we need to select our own toolchain
+        # by overriding 'custom_toolchain' and 'host_toolchain'.
+        # TODO: Is there a way to use it without the involvement of args.gn?
         if os.name == "nt":
-            out += [
-                'custom_toolchain="//build_extra/toolchain/win:win_clang_x64"'
-            ]
+            tc = "//build_extra/toolchain/win:win_clang_x64"
+            out += ['custom_toolchain="%s"' % tc, 'host_toolchain="%s"' % tc]
 
     print "DENO_BUILD_ARGS:", out