[runtime] Add support for finding assemblies in an RID-specific subdirectory.

runtime/product.h

@@ -6,6 +6,8 @@
 *
 */
 
+#include <TargetConditionals.h>
+
 #ifdef MONOTOUCH
   #if TARGET_OS_WATCH
 	#define PRODUCT                  "Xamarin.WatchOS"
@@ -43,4 +45,45 @@
 	#define ARCH_SUBDIR				
 #else
     #error Either MONOTOUCH or MONOMAC must be defined.
-#endif
+#endif
+
+// Set RuntimeIdentifier defines
+#if TARGET_OS_MACCATALYST
+  #define RUNTIMEIDENTIFIER_PLATFORM    "maccatalyst"
+#elif TARGET_OS_IOS
+  #if TARGET_OS_SIMULATOR
+    #define RUNTIMEIDENTIFIER_PLATFORM  "iossimulator"
+  #else
+    #define RUNTIMEIDENTIFIER_PLATFORM  "ios"
+  #endif
+#elif TARGET_OS_TV
+  #if TARGET_OS_SIMULATOR
+    #define RUNTIMEIDENTIFIER_PLATFORM  "tvossimulator"
+  #else
+    #define RUNTIMEIDENTIFIER_PLATFORM  "tvos"
+  #endif
+#elif TARGET_OS_WATCH
+  #if TARGET_OS_SIMULATOR
+    #define RUNTIMEIDENTIFIER_PLATFORM  "watchossimulator"
+  #else
+    #define RUNTIMEIDENTIFIER_PLATFORM  "watchos"
+  #endif
+#elif TARGET_OS_OSX
+  #define RUNTIMEIDENTIFIER_PLATFORM    "osx"
+#else
+  #error Unknown platform
+#endif
+
+#if defined (__aarch64__)
+  #define RUNTIMEIDENTIFIER_ARCHITECTURE "arm64"
+#elif defined (__x86_64__)
+  #define RUNTIMEIDENTIFIER_ARCHITECTURE "x64"
+#elif defined (__i386__)
+  #define RUNTIMEIDENTIFIER_ARCHITECTURE "x86"
+#elif defined (__arm__)
+  #define RUNTIMEIDENTIFIER_ARCHITECTURE "arm"
+#else
+    #error Unknown architecture
+#endif
+
+#define RUNTIMEIDENTIFIER RUNTIMEIDENTIFIER_PLATFORM "-" RUNTIMEIDENTIFIER_ARCHITECTURE

runtime/runtime.m

@@ -2478,7 +2478,7 @@ xamarin_vprintf (const char *format, va_list args)
  *
  * The platform assembly (Xamarin.[iOS|TVOS|WatchOS].dll) and any assemblies
  * the platform assembly references (mscorlib.dll, System.dll) may be in a
- * pointer-size subdirectory (ARCH_SUBDIR).
+ * pointer-size subdirectory (ARCH_SUBDIR), or an RID-specific subdirectory.
  * 
  * AOT data files will have an arch-specific infix.
  */
@@ -2536,6 +2536,16 @@ xamarin_locate_assembly_resource_for_root (const char *root, const char *culture
 	}
 #endif // !MONOMAC
 
+#if DOTNET
+	// RID-specific subdirectory
+	if (snprintf (path, pathlen, "%s/.xamarin/%s/%s", root, RUNTIMEIDENTIFIER, resource) < 0) {
+		LOG (PRODUCT ": Failed to construct path for resource: %s (5): %s", resource, strerror (errno));
+		return false;
+	} else if (xamarin_file_exists (path)) {
+		return true;
+	}
+#endif
+
 	// just the file, no extensions, etc.
 	if (snprintf (path, pathlen, "%s/%s", root, resource) < 0) {
 		LOG (PRODUCT ": Failed to construct path for resource: %s (6): %s", resource, strerror (errno));