Add ro.product.cpu.abi to Microdroid

ro.product.cpu.abi is deprecated [1] in favor of ro.product.cpu.abilist.
But tradefed test runner still depends on it.

[1] https://android.googlesource.com/platform/build/+/refs/heads/master/tools/buildinfo.sh#36

Bug: 221317917
Test: run Microdroid and check the sysprop value
Change-Id: I713cd12496ecbba19ed9344ce69c2d10e965f8be
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 81f94bc..0364896 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -168,7 +168,8 @@
         "grep ro\\.build\\.version\\.security_patch= $(location :buildinfo.prop) && " +
         "grep ro\\.build\\.version\\.known_codenames= $(location :buildinfo.prop) && " +
         "cat $(location build.prop) && " +
-        "echo ro.product.cpu.abilist=x86_64) > $(out)",
+        "echo ro.product.cpu.abilist=x86_64 && " +
+        "echo ro.product.cpu.abi=x86_64) > $(out)",
 }
 
 genrule {
@@ -185,7 +186,8 @@
         "grep ro\\.build\\.version\\.security_patch= $(location :buildinfo.prop) && " +
         "grep ro\\.build\\.version\\.known_codenames= $(location :buildinfo.prop) && " +
         "cat $(location build.prop) && " +
-        "echo ro.product.cpu.abilist=arm64-v8a) > $(out)",
+        "echo ro.product.cpu.abilist=arm64-v8a && " +
+        "echo ro.product.cpu.abi=arm64-v8a) > $(out)",
 }
 
 android_filesystem {