GN win: prep_libc and fix tcmalloc linkage

base/allocator/BUILD.gn

Index: base/allocator/BUILD.gn
diff --git a/base/allocator/BUILD.gn b/base/allocator/BUILD.gn
index ac29edf763466228978ca65e29f02f53b5d687d5..bbcd823cc1dd1d88fd5e00295f28c1dfa1193b60 100644
--- a/base/allocator/BUILD.gn
+++ b/base/allocator/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/allocator.gni")
+import("//build/config/win/visual_studio_version.gni")
 
 # Only executables and not libraries should depend on the allocator target;
 # only the application (the final executable) knows what allocator makes sense.
@@ -14,6 +15,14 @@ group("allocator") {
   }
 }
 
+config("nocmt") {
+  ldflags = [
+    "/NODEFAULTLIB:libcmt",
+    "/NODEFAULTLIB:libcmtd",
+  ]
+  libs = [ rebase_path("$target_gen_dir/allocator/libcmt.lib") ]
+}
+
 if (!is_android) {
   # tcmalloc currently won't compile on Android.
   source_set("tcmalloc") {
@@ -152,6 +161,21 @@ if (!is_android) {
         "$tcmalloc_dir/src/profiler.cc",
       ]
       defines += [ "PERFTOOLS_DLL_DECL=" ]
+
+      direct_dependent_configs = [ ":nocmt" ]
+
+      action("prep_libc") {

[brettw, 2014/05/17 02:38:37]

Can you avoid nesting targets? I've been wanting to disallow this. Nesting is
actually super confusing since all the sources and such will be inherited in
this case from the outer scope.

[scottmg, 2014/05/17 16:29:16]

OK, I'll do that.

It seems unfortunate to move this out -- it'd be nicer if it was 1) near the one
and only place it's used; 2) could be not-visible to anything in another scope.

+        script = "prep_libc.py"
+        outputs = [ "$target_gen_dir/allocator/libcmt.lib" ]
+        args = [
+          visual_studio_path + "/vc/lib",
+          rebase_path("$target_gen_dir/allocator"),
+          cpu_arch,
+        ]
+      }
+      deps = [
+        ":prep_libc",
+      ]
     }
     if (is_linux || is_android) {
       sources -= [
@@ -191,7 +215,7 @@ if (!is_android) {
       configs += [ "//build/config/compiler:optimize_max" ]
     }
 
-    deps = [
+    deps += [
       "//base/third_party/dynamic_annotations",
     ]