Fix more tests when ANDROID_BUILD_TOP is set

The bpfix code (also used by androidmk) reads the ANDROID_BUILD_TOP
environment variable, causing the tests to fail when it is set.  Clear
it in the bpfix and partner androidmk tests the same way the main
androidmk tests do.

Test: go test ./...
Change-Id: Icc61f2c3ebdbecab34c1d18399c6846db207c6dd

bpfix/bpfix/bpfix_test.go

@@ -19,6 +19,7 @@ package bpfix
 import (
 	"bytes"
 	"fmt"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
@@ -2215,3 +2216,9 @@ func TestRemoveResourceAndAssetsIfDefault(t *testing.T) {
 		})
 	}
 }
+
+func TestMain(m *testing.M) {
+	// Skip checking Android.mk path with cleaning "ANDROID_BUILD_TOP"
+	os.Setenv("ANDROID_BUILD_TOP", "")
+	os.Exit(m.Run())
+}

partner/androidmk/androidmk_test.go

@@ -54,6 +54,9 @@ cc_library_shared {
 }
 
 func TestEndToEnd(t *testing.T) {
+	// Skip checking Android.mk path with cleaning "ANDROID_BUILD_TOP"
+	t.Setenv("ANDROID_BUILD_TOP", "")
+
 	for i, test := range testCases {
 		expected, err := bpfix.Reformat(test.expected)
 		if err != nil {