Specify jnilib partition in Android-<target>.mk

Context
- Android-<target>.mk currently does not contain information about partition for its dependent unembedded jni libraries, but only lists the name of the unembedded jni libraries.
- If an android_app module depends on an unembedded jni library that is located in a different partition, make cannot find the library.

Implementation
- Create a string field partition in jniLib struct.
- Add variable "LOCAL_SOONG_JNI_LIBS_PARTITION_<target>", an array of mappings of the name of the jni library to its partition.

Bug: 154162945
Test: m
Change-Id: I6b8e1272ff59dc70e3dd6ce8c6c8e4686dad76df

android/paths.go

@@ -1638,6 +1638,10 @@ func (p InstallPath) PartitionDir() string {
 	}
 }
 
+func (p InstallPath) Partition() string {
+	return p.partition
+}
+
 // Join creates a new InstallPath with paths... joined with the current path. The
 // provided paths... may not use '..' to escape from the current path.
 func (p InstallPath) Join(ctx PathContext, paths ...string) InstallPath {