Export host available libraries to soong_injection

This information will be used to validate linkopts for host targets.

Test: m bp2build
Bug: 216626461
Change-Id: Ie7ac46268e6177cf0688ca0389bdaa92b67f9a58
diff --git a/cc/config/toolchain.go b/cc/config/toolchain.go
index 6a10e14..a0ef575 100644
--- a/cc/config/toolchain.go
+++ b/cc/config/toolchain.go
@@ -20,6 +20,12 @@
 	"android/soong/android"
 )
 
+func init() {
+	exportedVars.ExportStringListStaticVariable("DarwinAvailableLibraries", darwinAvailableLibraries)
+	exportedVars.ExportStringListStaticVariable("LinuxAvailableLibraries", linuxAvailableLibraries)
+	exportedVars.ExportStringListStaticVariable("WindowsAvailableLibraries", windowsAvailableLibraries)
+}
+
 type toolchainFactory func(arch android.Arch) Toolchain
 
 var toolchainFactories = make(map[android.OsType]map[android.ArchType]toolchainFactory)