Rework win_toolchains a bit and copy the vs runtime DLLs as needed.

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 a9fab7c4c03c422f9384ea48ce19404879015be6..8f2cbe0d984296cd954c65356434523e4bf416cd 100644
--- a/build/toolchain/win/BUILD.gn
+++ b/build/toolchain/win/BUILD.gn
@@ -25,6 +25,7 @@ concurrent_links = exec_script("../get_concurrent_links.py", [], "value")
 #  cpu_arch: cpu_arch to pass as a build arg
 #  environment: File name of environment file.
 #  force_win64 (optional): value for this build arg.
+#  TODO(dpranke): Get rid of force_win64?

[brettw, 2014/11/14 20:45:45]

You can delete this because you should get rid of it.

[Dirk Pranke, 2014/11/14 23:03:22]

Done.

 template("msvc_toolchain") {
   if (defined(invoker.concurrent_links)) {
     concurrent_links = invoker.concurrent_links
@@ -32,6 +33,16 @@ template("msvc_toolchain") {
 
   env = invoker.environment
 
+  if (is_debug) {
+    configuration = "Debug"
+  } else {
+    configuration = "Release"
+  }
+  exec_script("../../vs_toolchain.py", ["copy_dlls",
+                                        rebase_path(root_build_dir),
+                                        configuration,
+                                        invoker.cpu_arch])
+
   toolchain(target_name) {
     # Make these apply to all tools below.
     lib_switch = ""
@@ -164,13 +175,19 @@ template("msvc_toolchain") {
   }
 }
 
-msvc_toolchain("32") {
-  environment = "environment.x86"
-  cpu_arch = "x64"
+# TODO(dpranke): Declare both toolchains all of the time when we
+# get it sorted out how we want to support them both in a single build.

[scottmg, 2014/11/13 03:49:59]

note that only one of these can be enabled at a time because we can't have them
copying runtimes to the same place.

[Dirk Pranke, 2014/11/13 05:49:36]

Will do.

[Dirk Pranke, 2014/11/14 23:03:22]

Done.

+if (cpu_arch == "x86") {
+  msvc_toolchain("32") {
+    environment = "environment.x86"
+    cpu_arch = "x86"
+  }
 }
 
-msvc_toolchain("64") {
-  environment = "environment.x64"
-  cpu_arch = "x64"
-  force_win64 = true
+if (cpu_arch == "x64") {
+  msvc_toolchain("64") {
+    environment = "environment.x64"
+    cpu_arch = "x64"
+    force_win64 = true
+  }
 }