Improve sudo/kdesu error message

Now that you can get elevated privileges while using the app, we can
display a more useful and descriptive error message when people try to
run Dolphin using `sudo` or `kdesu`.

Also bump the frameworks dependency to 5.90 since that's the KIO
version that includes this change, so we can be sure that the message is
always accurate.

CMakeLists.txt

@@ -8,7 +8,7 @@ set (RELEASE_SERVICE_VERSION "${RELEASE_SERVICE_VERSION_MAJOR}.${RELEASE_SERVICE
 project(Dolphin VERSION ${RELEASE_SERVICE_VERSION})
 
 set(QT_MIN_VERSION "5.15.0")
-set(KF5_MIN_VERSION "5.89.0")
+set(KF5_MIN_VERSION "5.90.0")
 
 # ECM setup
 find_package(ECM ${KF5_MIN_VERSION} CONFIG REQUIRED)

src/main.cpp

@@ -44,10 +44,16 @@ int main(int argc, char **argv)
     // Prohibit using sudo or kdesu (but allow using the root user directly)
     if (getuid() == 0) {
         if (!qEnvironmentVariableIsEmpty("SUDO_USER")) {
-            std::cout << "Executing Dolphin with sudo is not possible due to unfixable security vulnerabilities." << std::endl;
+            std::cout << "Running Dolphin with sudo can cause bugs and expose you to security vulnerabilities. "
+                         "Instead use Dolphin normally and you will be prompted for elevated privileges when "
+                         "performing file operations that require them."
+                      << std::endl;
             return EXIT_FAILURE;
         } else if (!qEnvironmentVariableIsEmpty("KDESU_USER")) {
-            std::cout << "Executing Dolphin with kdesu is not possible due to unfixable security vulnerabilities." << std::endl;
+            std::cout << "Running Dolphin with kdesu can cause bugs and expose you to security vulnerabilities. "
+                         "Instead use Dolphin normally and you will be prompted for elevated privileges when "
+                         "performing file operations that require them."
+                      << std::endl;
             return EXIT_FAILURE;
         }
     }