[test] Enable linkViaSignatures based on directive, not target backend

We want to be able to use signature-based linkage in other kinds
of tests.

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/FirFrontendFacade.kt

@@ -278,6 +278,7 @@ open class FirFrontendFacade(
         val sessionProvider = moduleInfoProvider.firSessionProvider
 
         val project = compilerConfigurationProvider.getProject(module)
+        val compilerConfiguration = compilerConfigurationProvider.getCompilerConfiguration(module)
 
         PsiElementFinder.EP.getPoint(project).unregisterExtension(JavaElementFinder::class.java)
 
@@ -319,8 +320,8 @@ open class FirFrontendFacade(
             moduleBasedSession,
             Fir2IrConfiguration(
                 languageVersionSettings = module.languageVersionSettings,
-                linkViaSignatures = module.targetBackend == TargetBackend.JVM_IR_SERIALIZE,
-                evaluatedConstTracker = compilerConfigurationProvider.getCompilerConfiguration(module)
+                linkViaSignatures = compilerConfiguration.getBoolean(JVMConfigurationKeys.LINK_VIA_SIGNATURES),
+                evaluatedConstTracker = compilerConfiguration
                     .putIfAbsent(CommonConfigurationKeys.EVALUATED_CONST_TRACKER, EvaluatedConstTracker.create()),
             ),
             ktFiles,

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/runners/codegen/AbstractCompileKotlinAgainstInlineKotlinTest.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.test.directives.CodegenTestDirectives.IGNORE_BACKEND
 import org.jetbrains.kotlin.test.directives.CodegenTestDirectives.IGNORE_BACKEND_MULTI_MODULE
 import org.jetbrains.kotlin.test.FirParser
 import org.jetbrains.kotlin.test.directives.JvmEnvironmentConfigurationDirectives.SERIALIZE_IR
+import org.jetbrains.kotlin.test.directives.LanguageSettingsDirectives.LINK_VIA_SIGNATURES
 import org.jetbrains.kotlin.test.directives.configureFirParser
 import org.jetbrains.kotlin.test.directives.model.ValueDirective
 import org.jetbrains.kotlin.test.frontend.classic.ClassicFrontend2ClassicBackendConverter
@@ -90,6 +91,7 @@ open class AbstractIrCompileKotlinAgainstInlineKotlinTest :
 private fun TestConfigurationBuilder.configureForSerialization() {
     defaultDirectives {
         SERIALIZE_IR.with(JvmSerializeIrMode.INLINE)
+        +LINK_VIA_SIGNATURES
     }
 
     configureIrHandlersStep {