Move default crt objects into Toolchain

Move the crt objects spread around cc/library.go and cc/binary.go
into the Toolchain.  This will simplify adding new toolchains that
have custom crt objects.

Test: m checkbuild
Test: go test ./cc/...
Change-Id: I7fdc1f53769799cb9c10e3e5816dabee0f918768
diff --git a/cc/library.go b/cc/library.go
index 5b6c623..95f9b0a 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -1174,9 +1174,9 @@
 		deps.ReexportSharedLibHeaders = append(deps.ReexportSharedLibHeaders, library.StaticProperties.Static.Export_shared_lib_headers...)
 		deps.ReexportStaticLibHeaders = append(deps.ReexportStaticLibHeaders, library.StaticProperties.Static.Export_static_lib_headers...)
 	} else if library.shared() {
-		if ctx.toolchain().Bionic() && !Bool(library.baseLinker.Properties.Nocrt) {
-			deps.CrtBegin = []string{"crtbegin_so"}
-			deps.CrtEnd = []string{"crtend_so"}
+		if !Bool(library.baseLinker.Properties.Nocrt) {
+			deps.CrtBegin = append(deps.CrtBegin, ctx.toolchain().CrtBeginSharedLibrary()...)
+			deps.CrtEnd = append(deps.CrtEnd, ctx.toolchain().CrtEndSharedLibrary()...)
 		}
 		deps.WholeStaticLibs = append(deps.WholeStaticLibs, library.SharedProperties.Shared.Whole_static_libs...)
 		deps.StaticLibs = append(deps.StaticLibs, library.SharedProperties.Shared.Static_libs...)