refactor Bazel variable export

Most of the variable export code for cc modules can be re-used for
exporting variables for java modules. Refactor this code into a more
composable structure for reuse.

Test: build/bazel/bp2build.sh
Test: manual comparison of
  out/soong/soong_injection/cc_toolchain/constants.bzl
  with previous output
Change-Id: Ie5a6fee08cc888b7dc69c3e324e5c3f8aa269a8f
diff --git a/cc/config/x86_64_device.go b/cc/config/x86_64_device.go
index 164e7a6..aebda0b 100644
--- a/cc/config/x86_64_device.go
+++ b/cc/config/x86_64_device.go
@@ -91,26 +91,26 @@
 	pctx.SourcePathVariable("X86_64GccRoot",
 		"prebuilts/gcc/${HostPrebuiltTag}/x86/x86_64-linux-android-${x86_64GccVersion}")
 
-	exportStringListStaticVariable("X86_64ToolchainCflags", []string{"-m64"})
-	exportStringListStaticVariable("X86_64ToolchainLdflags", []string{"-m64"})
+	exportedVars.ExportStringListStaticVariable("X86_64ToolchainCflags", []string{"-m64"})
+	exportedVars.ExportStringListStaticVariable("X86_64ToolchainLdflags", []string{"-m64"})
 
-	exportStringListStaticVariable("X86_64Ldflags", x86_64Ldflags)
-	exportStringListStaticVariable("X86_64Lldflags", x86_64Ldflags)
+	exportedVars.ExportStringListStaticVariable("X86_64Ldflags", x86_64Ldflags)
+	exportedVars.ExportStringListStaticVariable("X86_64Lldflags", x86_64Ldflags)
 
 	// Clang cflags
-	exportStringListStaticVariable("X86_64Cflags", x86_64Cflags)
-	exportStringListStaticVariable("X86_64Cppflags", x86_64Cppflags)
+	exportedVars.ExportStringListStaticVariable("X86_64Cflags", x86_64Cflags)
+	exportedVars.ExportStringListStaticVariable("X86_64Cppflags", x86_64Cppflags)
 
 	// Yasm flags
-	exportStringListStaticVariable("X86_64YasmFlags", []string{
+	exportedVars.ExportStringListStaticVariable("X86_64YasmFlags", []string{
 		"-f elf64",
 		"-m amd64",
 	})
 
 	// Extended cflags
 
-	exportedStringListDictVars.Set("X86_64ArchVariantCflags", x86_64ArchVariantCflags)
-	exportedStringListDictVars.Set("X86_64ArchFeatureCflags", x86_64ArchFeatureCflags)
+	exportedVars.ExportStringListDict("X86_64ArchVariantCflags", x86_64ArchVariantCflags)
+	exportedVars.ExportStringListDict("X86_64ArchFeatureCflags", x86_64ArchFeatureCflags)
 
 	// Architecture variant cflags
 	for variant, cflags := range x86_64ArchVariantCflags {