fix: linker errors from mixing C (Utils.m) and C++ (Tweak.xm/JSI.mm) TUs

- Wrap Utils.h's declarations in extern "C" so Tweak.xm/JSI.mm link against
  the plain-C symbols Utils.m actually exports, instead of expecting
  C++-mangled names that don't exist (confirmed via CI: "Undefined symbols
  ... showErrorAlert(NSString*, NSString*)").
- Add -undefined dynamic_lookup (matching RainTweak's Makefile): JSI/Hermes
  symbols like jsi::JSError's typeinfo only exist in the host process's own
  compiled-in runtime once the tweak is actually loaded into Discord, not
  anywhere available to link against at build time.

Headers/Utils.h

@@ -1,9 +1,20 @@
 #import <Foundation/Foundation.h>
 #import <UIKit/UIKit.h>
 
+// Utils.m is compiled as plain Objective-C (C linkage), but Tweak.xm/JSI.mm are Objective-C++.
+// Without extern "C", the C++ TU expects a mangled `showErrorAlert(NSString*, NSString*)` symbol
+// that Utils.m never emits, breaking the link (confirmed by an actual Theos build on CI).
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 NSURL *getPyoncordDirectory(void);
 UIColor *hexToUIColor(NSString *hex);
 void showErrorAlert(NSString *title, NSString *message);
 
 /** Detects the Hermes bytecode magic header ("Herm"), as opposed to plain-text JS. */
 BOOL isHermesBytecode(NSData *data);
+
+#ifdef __cplusplus
+}
+#endif

Makefile

@@ -11,6 +11,9 @@ Revenge_FILES = $(wildcard Sources/*.x Sources/*.xm Sources/*.m Sources/*.mm Sou
 Revenge_CFLAGS = -fobjc-arc -DPACKAGE_VERSION='@"$(THEOS_PACKAGE_BASE_VERSION)"' -I$(THEOS_PROJECT_DIR)/Headers
 Revenge_CCFLAGS = -std=c++17 -Wno-c++11-narrowing -I$(THEOS_PROJECT_DIR)/Headers
 Revenge_FRAMEWORKS = Foundation UIKit CoreGraphics CoreText CoreFoundation
+# JSI types (e.g. jsi::JSError's typeinfo) only exist in the host process's own compiled-in
+# Hermes/JSI runtime, not anywhere we can statically link against - resolve at load time instead.
+Revenge_LDFLAGS = -undefined dynamic_lookup
 
 RevengeResources_INSTALL_PATH = "/Library/Application\ Support/"
 RevengeResources_RESOURCE_DIRS = Resources

Sources/Sideloading.x

@@ -47,7 +47,8 @@ static BOOL isSelfCall(void) {
 - (NSDictionary *)infoDictionary {
     if (!isSelfCall()) return %orig;
     
-    NSMutableDictionary *info = [%orig mutableCopy];
+    NSDictionary *origInfo = %orig;
+    NSMutableDictionary *info = [origInfo mutableCopy];
     info[@"CFBundleIdentifier"] = DISCORD_BUNDLE_ID;
     info[@"CFBundleDisplayName"] = DISCORD_NAME;
     info[@"CFBundleName"] = DISCORD_NAME;