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
diff --git a/apex/apex_test.go b/apex/apex_test.go
index 5c7c90b..6027f9b 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -4640,6 +4640,35 @@
 	}
 }
 
+func TestApexSetFilenameOverride(t *testing.T) {
+	testApex(t, `
+		apex_set {
+ 			name: "com.company.android.myapex",
+			apex_name: "com.android.myapex",
+			set: "company-myapex.apks",
+      filename: "com.company.android.myapex.apex"
+		}
+	`).ModuleForTests("com.company.android.myapex", "android_common_com.android.myapex")
+
+	testApex(t, `
+		apex_set {
+ 			name: "com.company.android.myapex",
+			apex_name: "com.android.myapex",
+			set: "company-myapex.apks",
+      filename: "com.company.android.myapex.capex"
+		}
+	`).ModuleForTests("com.company.android.myapex", "android_common_com.android.myapex")
+
+	testApexError(t, `filename should end in .apex or .capex for apex_set`, `
+		apex_set {
+ 			name: "com.company.android.myapex",
+			apex_name: "com.android.myapex",
+			set: "company-myapex.apks",
+      filename: "some-random-suffix"
+		}
+	`)
+}
+
 func TestPrebuiltOverrides(t *testing.T) {
 	ctx := testApex(t, `
 		prebuilt_apex {