clang/gn/win: Stop running the compiler through `ninja -t msvc -e environment.foo`

build/toolchain/win/BUILD.gn

Index: build/toolchain/win/BUILD.gn
diff --git a/build/toolchain/win/BUILD.gn b/build/toolchain/win/BUILD.gn
index 1934e9b19ad43287d8435364e318d8dd0b4b3d8f..be54376b9c4558a2f49439ea9dbcdcd26205884a 100644
--- a/build/toolchain/win/BUILD.gn
+++ b/build/toolchain/win/BUILD.gn
@@ -61,6 +61,7 @@ template("msvc_toolchain") {
   env = invoker.environment
 
   cl = invoker.cl
+  include_flags = invoker.include_flags
 
   toolchain(target_name) {
     # Make these apply to all tools below.
@@ -74,7 +75,7 @@ template("msvc_toolchain") {
       rspfile = "{{output}}.rsp"
       precompiled_header_type = "msvc"
       pdbname = "{{target_out_dir}}/{{label_name}}_c.pdb"
-      command = "ninja -t msvc -e $env -- $cl /nologo /showIncludes /FC @$rspfile /c {{source}} /Fo{{output}} /Fd$pdbname"
+      command = "$cl /nologo $include_flags /showIncludes /FC @$rspfile /c {{source}} /Fo{{output}} /Fd$pdbname"

[scottmg, 2016/02/25 03:40:15]

I don't understand how cl.exe gets PATH to be set properly in this case now. Or
are you saying it doesn't need that? Oh, maybe because we only use the x64 cross
or x64 native, we can get away without adding any directories?

[Nico, 2016/02/25 03:45:41]

We don't need the path. cl is set to `cl =
"${goma_prefix}\"${x86_toolchain_data.vc_bin_dir}/cl.exe\""` below, which is a
qualified path to cl. cl doesn't invoke any subprograms (or looks at them
relative to itself). vc_bin_dir is also returned by setup_toolchain.py

[scottmg, 2016/02/25 18:16:23]

Are you sure? Looking in VC\bin\amd64_x86, there's a compiler and its direct
DLLs, but other DLLs like msobj120.dll and mspdb120.dll that I believe it needs
to load are only in the root (x86) dir and in amd64.

       depsformat = "msvc"
       description = "CC {{output}}"
       outputs = [
@@ -89,7 +90,7 @@ template("msvc_toolchain") {
 
       # The PDB name needs to be different between C and C++ compiled files.
       pdbname = "{{target_out_dir}}/{{label_name}}_cc.pdb"
-      command = "ninja -t msvc -e $env -- $cl /nologo /showIncludes /FC @$rspfile /c {{source}} /Fo{{output}} /Fd$pdbname"
+      command = "$cl /nologo $include_flags /showIncludes /FC @$rspfile /c {{source}} /Fo{{output}} /Fd$pdbname"
       depsformat = "msvc"
       description = "CXX {{output}}"
       outputs = [
@@ -239,6 +240,13 @@ template("msvc_toolchain") {
   }
 }
 
+if (is_clang) {
+  sys_include_prefix = "-isystem="
+} else {
+  # MSVC doesn't have the concept of system headers.
+  sys_include_prefix = "/I"
+}
+
 if (host_os == "win") {
   clang_cl = "clang-cl.exe"
 } else {
@@ -256,6 +264,7 @@ if (target_cpu == "x86") {
                                      windows_sdk_path,
                                      visual_studio_runtime_dirs,
                                      "x86",
+                                     "${sys_include_prefix}",
                                    ],
                                    "scope")
 
@@ -264,6 +273,7 @@ if (target_cpu == "x86") {
     toolchain_cpu = "x86"
     cl = "${goma_prefix}\"${x86_toolchain_data.vc_bin_dir}/cl.exe\""
     is_clang = false
+    include_flags = "${x86_toolchain_data.include_flags}"
   }
 
   msvc_toolchain("clang_x86") {
@@ -274,6 +284,7 @@ if (target_cpu == "x86") {
     cl = "${goma_prefix}$prefix/${clang_cl}"
     toolchain_os = "win"
     is_clang = true
+    include_flags = "${x86_toolchain_data.include_flags}"
   }
 }
 
@@ -285,6 +296,7 @@ x64_toolchain_data = exec_script("setup_toolchain.py",
                                    windows_sdk_path,
                                    visual_studio_runtime_dirs,
                                    "x64",
+                                   "${sys_include_prefix}",
                                  ],
                                  "scope")
 
@@ -301,6 +313,7 @@ template("win_x64_toolchains") {
     toolchain_cpu = "x64"
     cl = "${goma_prefix}\"${x64_toolchain_data.vc_bin_dir}/cl.exe\""
     is_clang = false
+    include_flags = "${x64_toolchain_data.include_flags}"
 
     forward_variables_from(invoker, [ "is_component_build" ])
   }
@@ -313,6 +326,7 @@ template("win_x64_toolchains") {
     cl = "${goma_prefix}$prefix/${clang_cl}"
     toolchain_os = "win"
     is_clang = true
+    include_flags = "${x64_toolchain_data.include_flags}"
 
     forward_variables_from(invoker, [ "is_component_build" ])
   }