gn: Fix build issues blocking gfx from being built

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 ba25fe47397228e26c1993a4abcc5f25bc9aac6c..34bf92af6ccf515457a4a5039af6633296edd0a7 100644
--- a/build/toolchain/win/BUILD.gn
+++ b/build/toolchain/win/BUILD.gn
@@ -111,6 +111,8 @@ template("msvc_toolchain") {
         dllname,
         libname,
       ]
+      link_output = dllname

[ckocagil, 2014/09/21 02:05:05]

These should be explicitly stated, otherwise it uses outputs[0] (dllname) for
both outputs, so it will try linking base.dll instead of base.dll.lib.

[brettw, 2014/09/21 02:55:00]

Actually, I think both of these should be the .lib. This trick with doing a
different dependency and link output file doesn't work on Windows. Our link
lines should basically match the GYP ones.

[ckocagil, 2014/09/21 11:47:26]

Done. But could you elaborate on how it doesn't work on Win? Does it not
correctly rebuild if either/both linker outputs are deleted?

+      depend_output = libname
       # The use of inputs_newline is to work around a fixed per-line buffer
       # size in the linker.
       rspfile_content = "{{libs}} {{solibs}} {{inputs_newline}} {{ldflags}}"