Add ramdisk image.

It is similar to recovery image.
Test: m nothing -j

Change-Id: I11389777c6bfb0c0d73bbb4c70091c1e70f44077

android/paths_test.go

@@ -202,6 +202,7 @@ type moduleInstallPathContextImpl struct {
 	inData         bool
 	inTestcases    bool
 	inSanitizerDir bool
+	inRamdisk      bool
 	inRecovery     bool
 	inRoot         bool
 }
@@ -224,6 +225,10 @@ func (m moduleInstallPathContextImpl) InstallInSanitizerDir() bool {
 	return m.inSanitizerDir
 }
 
+func (m moduleInstallPathContextImpl) InstallInRamdisk() bool {
+	return m.inRamdisk
+}
+
 func (m moduleInstallPathContextImpl) InstallInRecovery() bool {
 	return m.inRecovery
 }