Compile standalone system server jars.

This CL updates odrefresh to take an additional environment variable
`STANDALONE_SYSTEMSERVER_JARS` and compile standalone system server jars
accordingly.

Bug: 203198541
Test: atest odsign_e2e_tests
Test: atest art_standalone_odrefresh_tests
Test: atest art_standalone_artd_tests
Test: manual -
  1. Patch aosp/1874113, aosp/1876173, aosp/1875774 and aosp/1875775.
  2. Build a new system image and flash it to a device.
  3. adb logcat odrefresh:D odsign:D "*:S"
  4. See standalone system server jars being compiled and signed.

Change-Id: Ic824c7380cf9530437bc2a95b9ff816a63b22013
diff --git a/odrefresh/CacheInfo.xsd b/odrefresh/CacheInfo.xsd
index 44f733f..3aa94a5 100644
--- a/odrefresh/CacheInfo.xsd
+++ b/odrefresh/CacheInfo.xsd
@@ -29,7 +29,7 @@
       <xs:element name="moduleInfoList" minOccurs="1" maxOccurs="1" type="t:moduleInfoList" />
       <xs:element name="bootClasspath" minOccurs="1" maxOccurs="1" type="t:classpath" />
       <xs:element name="dex2oatBootClasspath" minOccurs="1" maxOccurs="1" type="t:classpath" />
-      <xs:element name="systemServerClasspath" minOccurs="1" maxOccurs="1" type="t:classpath" />
+      <xs:element name="systemServerComponents" minOccurs="1" maxOccurs="1" type="t:systemServerComponents" />
     </xs:sequence>
     </xs:complexType>
   </xs:element>
@@ -69,4 +69,20 @@
     <xs:attribute name="checksums" type="xs:string" use="required" />
   </xs:complexType>
 
+  <xs:complexType name="systemServerComponents">
+    <xs:sequence>
+      <xs:element name="component" type="t:systemServerComponent" />
+    </xs:sequence>
+  </xs:complexType>
+
+  <xs:complexType name="systemServerComponent">
+    <xs:complexContent>
+      <xs:extension base="component">
+        <!-- True if the component is in SYSTEMSERVERCLASSPATH. Otherwise, the component is a
+          standalone one. -->
+        <xs:attribute name="isInClasspath" type="xs:boolean" use="required" />
+      </xs:extension>
+    </xs:complexContent>
+  </xs:complexType>
+
 </xs:schema>