Relax restriction on suffix of apex_set filename to include .capex

Compressed APEX files generated by the build system have the .capex
extension. This CL allows us using those .capex files with their actual
suffix.

Bug: 197258691
Test: manual + unit test added
Change-Id: I79173ef942326b48b5e659f1873d80f12b212339

apex/androidmk.go

@@ -382,7 +382,7 @@ func (a *apexBundle) androidMkForType() android.AndroidMkData {
 				fmt.Fprintln(w, "LOCAL_MODULE_PATH :=", a.installDir.ToMakePath().String())
 				stemSuffix := apexType.suffix()
 				if a.isCompressed {
-					stemSuffix = ".capex"
+					stemSuffix = imageCapexSuffix
 				}
 				fmt.Fprintln(w, "LOCAL_MODULE_STEM :=", name+stemSuffix)
 				fmt.Fprintln(w, "LOCAL_UNINSTALLABLE_MODULE :=", !a.installable())