bp2build: export some cc toolchain flags into Starlark.

This CL exports common/global/device/host clang/ld/ldd flags
from their Ninja variable initialization locations in
cc/config/global.go and cc/config/clang.go to make Bazel's cc_toolchain
and Soong's cc actions more consistent with each other.

This does not handle env-dependent or arch-specific toolchain flags
yet (logic in compiler.go and linker.go).

Test: TH
Bug: 187086342
Bug: 187084737
Bug: 186628704
Bug: 187857770
Change-Id: Ie403d7cd23f35160897b9dd902c799cbf1bd7f0c
diff --git a/bp2build/conversion.go b/bp2build/conversion.go
index d67ab3d..eb83b38 100644
--- a/bp2build/conversion.go
+++ b/bp2build/conversion.go
@@ -2,6 +2,7 @@
 
 import (
 	"android/soong/android"
+	"android/soong/cc/config"
 	"fmt"
 	"reflect"
 	"sort"
@@ -16,6 +17,15 @@
 	Contents string
 }
 
+func CreateSoongInjectionFiles() []BazelFile {
+	var files []BazelFile
+
+	files = append(files, newFile("cc_toolchain", "BUILD", "")) // Creates a //cc_toolchain package.
+	files = append(files, newFile("cc_toolchain", "constants.bzl", config.BazelCcToolchainVars()))
+
+	return files
+}
+
 func CreateBazelFiles(
 	ruleShims map[string]RuleShim,
 	buildToTargets map[string]BazelTargets,