Support env based compiler flags.

Bug: 187086342
Test: Manual and unit tests.
Change-Id: Ic8e5f09dd6552e1121174bb00f0aae647661cf7b
diff --git a/cc/config/global.go b/cc/config/global.go
index a4e2975..c0f6e77 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -344,16 +344,7 @@
 	exportedVars.ExportStringListStaticVariable("HostGlobalLldflags", hostGlobalLldflags)
 
 	// Export the static default CommonGlobalCflags to Bazel.
-	// TODO(187086342): handle cflags that are set in VariableFuncs.
-	bazelCommonGlobalCflags := append(
-		commonGlobalCflags,
-		[]string{
-			// Default to zero initialization.
-			"-ftrivial-auto-var-init=zero",
-			"-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang",
-			"-Wno-unused-command-line-argument",
-		}...)
-	exportedVars.ExportStringList("CommonGlobalCflags", bazelCommonGlobalCflags)
+	exportedVars.ExportStringList("CommonGlobalCflags", commonGlobalCflags)
 
 	pctx.VariableFunc("CommonGlobalCflags", func(ctx android.PackageVarContext) string {
 		flags := commonGlobalCflags