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/sh/sh_binary_test.go b/sh/sh_binary_test.go
index 20317d8..865d5f3 100644
--- a/sh/sh_binary_test.go
+++ b/sh/sh_binary_test.go
@@ -115,7 +115,7 @@
 		}
 	`)
 
-	buildOS := android.BuildOs.String()
+	buildOS := config.BuildOS.String()
 	arches := []string{"android_arm64_armv8-a", buildOS + "_x86_64"}
 	for _, arch := range arches {
 		variant := ctx.ModuleForTests("foo", arch)
@@ -155,7 +155,7 @@
 		}
 	`)
 
-	buildOS := android.BuildOs.String()
+	buildOS := ctx.Config().BuildOS.String()
 	mod := ctx.ModuleForTests("foo", buildOS+"_x86_64").Module().(*ShTest)
 	if !mod.Host() {
 		t.Errorf("host bit is not set for a sh_test_host module.")
@@ -192,7 +192,7 @@
 		}
 	`)
 
-	buildOS := android.BuildOs.String()
+	buildOS := config.BuildOS.String()
 	variant := ctx.ModuleForTests("foo", buildOS+"_x86_64")
 
 	relocated := variant.Output("relocated/lib64/libbar.so")