Add sysroot property for sysroots.

Bug: 168729404
Test: make
Change-Id: I526742d3be83cd4f3bbe0b44890c9203e85829b9
diff --git a/linux-x86/Android.bp b/linux-x86/Android.bp
index 2096220..0eec23d 100644
--- a/linux-x86/Android.bp
+++ b/linux-x86/Android.bp
@@ -17,6 +17,7 @@
     },
     enabled: false,
     host_supported: true,
+    sysroot: true,
 }
 
 rust_prebuilt_library {
@@ -38,4 +39,5 @@
     },
     enabled: false,
     host_supported: true,
+    sysroot: true,
 }