Generate a StaticLibrary for rlibs and DynamicLibrary for proc macros

Teaches GN to be able to generate VS ide files when Rust-specific
target types are present.

Bug: 339
Change-Id: Ie07ac45e13686d5f7f49be33b817df68e787ceea
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/15620
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Reviewed-by: Dana Jansens <danakj@google.com>

src/gn/visual_studio_writer.cc

diff --git a/src/gn/visual_studio_writer.cc b/src/gn/visual_studio_writer.cc
index f567d36..31c6e0a 100644
--- a/src/gn/visual_studio_writer.cc
+++ b/src/gn/visual_studio_writer.cc
@@ -134,9 +134,11 @@
       return "Application";
     case Target::SHARED_LIBRARY:
     case Target::LOADABLE_MODULE:
+    case Target::RUST_PROC_MACRO:
       return "DynamicLibrary";
     case Target::STATIC_LIBRARY:
     case Target::SOURCE_SET:
+    case Target::RUST_LIBRARY:
       return "StaticLibrary";
     case Target::GROUP:
       return "Utility";