Replace android.BuildOs with Config.BuildOS

Replace the android.BuildOs constant with Config.BuildOS so that it
can vary based on the product config.

Bug: 190084016
Test: all Soong tests
Change-Id: Ia67f872d8b2ab788747a22e3a9659dc21c9775cd
diff --git a/cc/config/global.go b/cc/config/global.go
index dfbe6c4..55e0d79 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -15,6 +15,7 @@
 package config
 
 import (
+	"runtime"
 	"strings"
 
 	"android/soong/android"
@@ -282,7 +283,7 @@
 var pctx = android.NewPackageContext("android/soong/cc/config")
 
 func init() {
-	if android.BuildOs == android.Linux {
+	if runtime.GOOS == "linux" {
 		commonGlobalCflags = append(commonGlobalCflags, "-fdebug-prefix-map=/proc/self/cwd=")
 	}
 
diff --git a/cc/makevars.go b/cc/makevars.go
index 393170a..8d7a163 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -165,7 +165,7 @@
 	sort.Strings(ndkKnownLibs)
 	ctx.Strict("NDK_KNOWN_LIBS", strings.Join(ndkKnownLibs, " "))
 
-	hostTargets := ctx.Config().Targets[android.BuildOs]
+	hostTargets := ctx.Config().Targets[ctx.Config().BuildOS]
 	makeVarsToolchain(ctx, "", hostTargets[0])
 	if len(hostTargets) > 1 {
 		makeVarsToolchain(ctx, "2ND_", hostTargets[1])
diff --git a/cc/prebuilt_test.go b/cc/prebuilt_test.go
index fa6dd87..c8f8103 100644
--- a/cc/prebuilt_test.go
+++ b/cc/prebuilt_test.go
@@ -15,6 +15,7 @@
 package cc
 
 import (
+	"runtime"
 	"testing"
 
 	"android/soong/android"
@@ -271,8 +272,8 @@
 }
 
 func TestPrebuiltSymlinkedHostBinary(t *testing.T) {
-	if android.BuildOs != android.Linux {
-		t.Skipf("Skipping host prebuilt testing that is only supported on %s not %s", android.Linux, android.BuildOs)
+	if runtime.GOOS != "linux" {
+		t.Skipf("Skipping host prebuilt testing that is only supported on linux not %s", runtime.GOOS)
 	}
 
 	ctx := testPrebuilt(t, `
diff --git a/cc/proto_test.go b/cc/proto_test.go
index b9c89c7..abcb273 100644
--- a/cc/proto_test.go
+++ b/cc/proto_test.go
@@ -51,7 +51,7 @@
 			},
 		}`)
 
-		buildOS := android.BuildOs.String()
+		buildOS := ctx.Config().BuildOS.String()
 
 		proto := ctx.ModuleForTests("libfoo", "android_arm_armv7-a-neon_shared").Output("proto/a.pb.cc")
 		foobar := ctx.ModuleForTests("protoc-gen-foobar", buildOS+"_x86_64")