Separate dexpreopt.GlobalSoongConfig to allow independent caching of

it.

Introduce a Once cache for GlobalSoongConfig to allow it to get binary
tool paths from ordinary module dependencies (coming in a future CL)
that are then reused in singletons.

Bug: 145934348
Test: m
Change-Id: I440a09dba7d337965a196527566b0966a18e3653

java/java_test.go

@@ -57,7 +57,13 @@ func TestMain(m *testing.M) {
 }
 
 func testConfig(env map[string]string, bp string, fs map[string][]byte) android.Config {
-	return TestConfig(buildDir, env, bp, fs)
+	config := TestConfig(buildDir, env, bp, fs)
+
+	// Set up the global Once cache used for dexpreopt.GlobalSoongConfig, so that
+	// it doesn't create a real one, which would fail.
+	_ = dexpreopt.GlobalSoongConfigForTests(config)
+
+	return config
 }
 
 func testContext() *android.TestContext {