cc: clearer OS mismatch error.

Bugs: me
Test: clear error message, for instance:

    error: frameworks/native/libs/binder/ndk/Android.bp:252:1: module "libbinder_ndk.ndk" variant "android_x86_64_silvermont_sdk_shared_29": OS mismatch between "libbinder_ndk.ndk" (android) and "libbinder_headers_platform_shared" (linux_glibc)

Change-Id: Idfa6d27daeb89056781c93a893e4080e49b3fcb0
diff --git a/cc/cc.go b/cc/cc.go
index 947dc1a..927935c 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -3042,7 +3042,7 @@
 		}
 
 		if dep.Target().Os != ctx.Os() {
-			ctx.ModuleErrorf("OS mismatch between %q and %q", ctx.ModuleName(), depName)
+			ctx.ModuleErrorf("OS mismatch between %q (%s) and %q (%s)", ctx.ModuleName(), ctx.Os().Name, depName, dep.Target().Os.Name)
 			return
 		}
 		if dep.Target().Arch.ArchType != ctx.Arch().ArchType {