Add Path.Base helper

Add Path.Base to return the basename of a Path object.

Test: builds
Change-Id: I2bf1519dc5039bedb1586e7ec18297a293e32e11

android/paths.go

@@ -79,8 +79,11 @@ type Path interface {
 	// Returns the path in string form
 	String() string
 
-	// Returns the current file extension of the path
+	// Ext returns the extension of the last element of the path
 	Ext() string
+
+	// Base returns the last element of the path
+	Base() string
 }
 
 // WritablePath is a type of path that can be used as an output for build rules.
@@ -284,6 +287,10 @@ func (p basePath) Ext() string {
 	return filepath.Ext(p.path)
 }
 
+func (p basePath) Base() string {
+	return filepath.Base(p.path)
+}
+
 // SourcePath is a Path representing a file path rooted from SrcDir
 type SourcePath struct {
 	basePath