Fix new build warnings in Core with Xcode 12.5 (#7431)

FirebaseCore/CHANGELOG.md

@@ -1,3 +1,6 @@
+# FirebaseCore 7.6.0
+- [fixed] Fixed build warnings introduced with Xcode 12.5. (#7431)
+
 # Firebase 7.5.0
 - [fixed] Fixed potential deadlock with objc_copyImageNames call. (#7310)
 

FirebaseCore/Sources/FIRLogger.m

@@ -55,7 +55,7 @@ static NSString *const kMessageCodePattern = @"^I-[A-Z]{3}[0-9]{6}$";
 static NSRegularExpression *sMessageCodeRegex;
 #endif
 
-void FIRLoggerInitializeASL() {
+void FIRLoggerInitializeASL(void) {
   dispatch_once(&sFIRLoggerOnceToken, ^{
     // Register Firebase Version with GULLogger.
     GULLoggerRegisterVersion(FIRFirebaseVersion());
@@ -98,7 +98,7 @@ void FIRSetLoggerLevel(FIRLoggerLevel loggerLevel) {
 }
 
 #ifdef DEBUG
-void FIRResetLogger() {
+void FIRResetLogger(void) {
   extern void GULResetLogger(void);
   sFIRLoggerOnceToken = 0;
   [sFIRLoggerUserDefaults removeObjectForKey:kFIRPersistedDebugModeKey];