dxc: make "dxcompiler" target a shared_library

Instead of a loadable_module, so that it produces "libdxcompiler.dylib"
on MacOS, rather than "dxcompiler.so". This mimics what happens in the
CMake build, and our tooling expects a dylib on MacOS.

Change-Id: Ifaa27ec4f8fcfa692cc7137bc34487f3440459f7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/213034
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
diff --git a/third_party/gn/dxc/BUILD.gn b/third_party/gn/dxc/BUILD.gn
index 4ae3d74..06b7446 100644
--- a/third_party/gn/dxc/BUILD.gn
+++ b/third_party/gn/dxc/BUILD.gn
@@ -2323,7 +2323,7 @@
   sources = [ "$dawn_dxc_dir/resources/windows_version_resource.rc" ]
 }
 
-loadable_module("dxcompiler") {
+shared_library("dxcompiler") {
   if (dawn_has_build) {
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]