Remove clang indirection without affecting build.ninja

Remove cflags that are not handled by clang from the global defaults,
and remove calls to ClangFilterUnknownCflags.

Squash lists of clang-specific default flags into the main default
flags lists.

Rename Toolchain.Clang*flags to Toolchain.*flags.

Rename Go variables with Clang in the name that have no non-Clang
equivalent.

Remove unused ninja variables.

Bug: 68947919
Test: no change to build.ninja for aosp_cf_x86_64_phone-userdebug or aosp_crosshatch-userdebug
Change-Id: Id287945315d53e5eaef197adbbb4f1302f2e3680
diff --git a/cc/linker.go b/cc/linker.go
index 13df232..a712391 100644
--- a/cc/linker.go
+++ b/cc/linker.go
@@ -479,9 +479,9 @@
 	}
 
 	if linker.useClangLld(ctx) {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.ClangLldflags())
+		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.Lldflags())
 	} else {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.ClangLdflags())
+		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.Ldflags())
 	}
 
 	if !ctx.toolchain().Bionic() && !ctx.Fuchsia() {
@@ -535,7 +535,7 @@
 		flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,--hash-style=both")
 	}
 
-	flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.ToolchainClangLdflags())
+	flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.ToolchainLdflags())
 
 	if Bool(linker.Properties.Group_static_libs) {
 		flags.GroupStaticLibs = true