[build scripts] introduce ProductProperties.rootModuleForModularLoader property instead of supportModularLoading (RDCT-1034)

This way we can explicitly specify which root module should be used for different variants of JetBrains Client. Before, 'applicationInfoModule' property was used for that. It was confusing and also required copying the JetBrainsClientApplicationInfo.xml file to the custom root module.

GitOrigin-RevId: cadd910e880db6525fc3d083eb3f3cb90e69c666

platform/build-scripts/src/org/jetbrains/intellij/build/BuildContext.kt

@@ -65,7 +65,7 @@ interface BuildContext : CompilationContext {
   val ideMainClassName: String
 
   /**
-   * Specifies whether the new modular loader should be used in the IDE distributions, see [ProductProperties.supportModularLoading] and
+   * Specifies whether the new modular loader should be used in the IDE distributions, see [ProductProperties.rootModuleForModularLoader] and
    * [BuildOptions.useModularLoader].
    */
   val useModularLoader: Boolean

platform/build-scripts/src/org/jetbrains/intellij/build/BuildOptions.kt

@@ -379,8 +379,8 @@ data class BuildOptions(
   val nonBundledPluginDirectoriesToInclude: Set<String> = getSetProperty("intellij.build.non.bundled.plugin.dirs.to.include")
 
   /**
-   * If this option and [ProductProperties.supportModularLoading] are set to `true`, a file containing module descriptors will be added to
-   * the distribution (IJPL-109), and launchers will use it to start the IDE (IJPL-128).
+   * If this option is set to `true` and [ProductProperties.rootModuleForModularLoader] is non-null, a file containing module descriptors 
+   * will be added to the distribution (IJPL-109), and launchers will use it to start the IDE (IJPL-128).
    */
   @ApiStatus.Experimental
   var useModularLoader: Boolean = SystemProperties.getBooleanProperty("intellij.build.use.modular.loader", true)

platform/build-scripts/src/org/jetbrains/intellij/build/ProductProperties.kt

@@ -187,13 +187,6 @@ abstract class ProductProperties {
    */
   var buildCrossPlatformDistribution: Boolean = false
 
-  /**
-   * Set to `true` if the product can be started using [com.intellij.platform.runtime.loader.IntellijLoader]. 
-   * [BuildOptions.useModularLoader] will be used to determine whether the produced distribution will actually use this way.
-   */
-  @ApiStatus.Experimental
-  var supportModularLoading: Boolean = false
-
   /**
    * Specifies the main module of JetBrains Client product which distribution should be embedded into the IDE's distribution to allow 
    * running JetBrains Client. 
@@ -209,10 +202,17 @@ abstract class ProductProperties {
   @ApiStatus.Experimental
   var embeddedJetBrainsClientProperties: (() -> ProductProperties)? = null
 
+  /**
+   * Set to the root product module (the one containing product-modules.xml file) to enable using module-based loader for the product. 
+   * [BuildOptions.useModularLoader] will be used to determine whether the produced distribution will actually use this way.
+   */
+  @ApiStatus.Experimental
+  var rootModuleForModularLoader: String? = null
+
   /**
    * Specifies the mode of this product which will be used to determine which plugin modules should be loaded at runtime by 
    * [the modular loader][com.intellij.platform.bootstrap.ModuleBasedProductLoadingStrategy].
-   * This property makes sense only if [supportModularLoading] is set to `true`.
+   * This property makes sense only if [rootModuleForModularLoader] is set to a non-null value.
    */
   @ApiStatus.Experimental
   var productMode: ProductMode = ProductMode.LOCAL_IDE

platform/build-scripts/src/org/jetbrains/intellij/build/impl/BuildContextImpl.kt

@@ -79,7 +79,7 @@ class BuildContextImpl(
     get() = if (useModularLoader) "com.intellij.platform.runtime.loader.IntellijLoader" else productProperties.mainClassName
   
   override val useModularLoader: Boolean
-    get() = productProperties.supportModularLoading && options.useModularLoader
+    get() = productProperties.rootModuleForModularLoader != null && options.useModularLoader
 
   override val generateRuntimeModuleRepository: Boolean
     get() = useModularLoader || isEmbeddedJetBrainsClientEnabled && options.generateRuntimeModuleRepository
@@ -323,7 +323,7 @@ class BuildContextImpl(
       jvmArgs.add("-Dintellij.platform.runtime.repository.path=${macroName}/${MODULE_DESCRIPTORS_JAR_PATH}".let { if (isScript) '"' + it + '"' else it })
     }
     if (useModularLoader) {
-      jvmArgs.add("-Dintellij.platform.root.module=${productProperties.applicationInfoModule}")
+      jvmArgs.add("-Dintellij.platform.root.module=${productProperties.rootModuleForModularLoader!!}")
       jvmArgs.add("-Dintellij.platform.product.mode=${productProperties.productMode.id}")
     }