Remove "exported" ninja variables

There was infrastructure to export ninja variables to bazel. Now that
the bazel migration is cancelled, we don't need it anymore.

Bug: 315353489
Test: m nothing
Change-Id: I298cc2ac7ebd004557be3b30d75f7357cab0b7a0
diff --git a/cc/config/toolchain.go b/cc/config/toolchain.go
index 71e98fe..7dc990b 100644
--- a/cc/config/toolchain.go
+++ b/cc/config/toolchain.go
@@ -16,14 +16,15 @@
 
 import (
 	"fmt"
+	"strings"
 
 	"android/soong/android"
 )
 
 func init() {
-	exportedVars.ExportStringListStaticVariable("DarwinAvailableLibraries", darwinAvailableLibraries)
-	exportedVars.ExportStringListStaticVariable("LinuxAvailableLibraries", linuxAvailableLibraries)
-	exportedVars.ExportStringListStaticVariable("WindowsAvailableLibraries", windowsAvailableLibraries)
+	pctx.StaticVariable("DarwinAvailableLibraries", strings.Join(darwinAvailableLibraries, " "))
+	pctx.StaticVariable("LinuxAvailableLibraries", strings.Join(linuxAvailableLibraries, " "))
+	pctx.StaticVariable("WindowsAvailableLibraries", strings.Join(windowsAvailableLibraries, " "))
 }
 
 type toolchainFactory func(arch android.Arch) Toolchain