Fix tests with cc_binary_host on mac

cc_binary_host on mac uses ctx.Config().HostSystemTool(), which needs
PATH in the test environment.  Copy it from the original environment.

Fixes: 129763458
Test: proto_test.go
Change-Id: I41c1acdceee7c35036148256adafb471871034df

android/config.go

@@ -198,6 +198,14 @@ func saveToConfigFile(config jsonConfigurable, filename string) error {
 
 // TestConfig returns a Config object suitable for using for tests
 func TestConfig(buildDir string, env map[string]string) Config {
+	envCopy := make(map[string]string)
+	for k, v := range env {
+		envCopy[k] = v
+	}
+
+	// Copy the real PATH value to the test environment, it's needed by HostSystemTool() used in x86_darwin_host.go
+	envCopy["PATH"] = originalEnv["PATH"]
+
 	config := &config{
 		productVariables: productVariables{
 			DeviceName:                  stringPtr("test_device"),
@@ -212,7 +220,7 @@ func TestConfig(buildDir string, env map[string]string) Config {
 
 		buildDir:     buildDir,
 		captureBuild: true,
-		env:          env,
+		env:          envCopy,
 	}
 	config.deviceConfig = &deviceConfig{
 		config: config,

cc/proto_test.go

@@ -15,7 +15,6 @@
 package cc
 
 import (
-	"runtime"
 	"strings"
 	"testing"
 
@@ -38,9 +37,6 @@ func TestProto(t *testing.T) {
 	})
 
 	t.Run("plugin", func(t *testing.T) {
-		if runtime.GOOS != "linux" {
-			t.Skip("TODO(b/129763458): cc_binary_host tests fail on mac when trying to exec xcrun")
-		}
 		ctx := testCc(t, `
 		cc_binary_host {
 			name: "protoc-gen-foobar",