fix: XCode 26.4 compatibility (#1438)

## 📜 Description

Fixed compilation errors when compiling app with XCode 26.4

## 💡 Motivation and Context

The easiest fix is to force necessary C++ version in postinstall script.
We can keep it for now, but when upgrade to RN 0.85+ it can be safely
removed 🤞

## 📢 Changelog

<!-- High level overview of important changes -->
<!-- For example: fixed status bar manipulation; added new types
declarations; -->
<!-- If your changes don't affect one of platform/language below - then
remove this platform/language -->

### Example

- force C++17 standard for `fmt`;

## 🤔 How Has This Been Tested?

Tested on iPhone 17 Pro (iOS 26.4) with XCode 26.4.

## 📸 Screenshots (if appropriate):

|Before|After|
|-------|-----|
|<img width="274" height="567" alt="Screenshot 2026-04-16 at 16 15 54"
src="https://github.com/user-attachments/assets/448a777e-d992-4e39-93e9-9eaed60a1ae9"
/>|<img width="285" height="636" alt="image"
src="https://github.com/user-attachments/assets/179d5f76-5101-41b3-b1ea-61a498a51f6c"
/>|

## 📝 Checklist

- [x] CI successfully passed
- [x] I added new mocks and corresponding unit-tests if library API was
changed

Author: kirillzyusko

FabricExample/ios/Podfile

@@ -33,5 +33,14 @@ target 'KeyboardControllerFabricExample' do
       :mac_catalyst_enabled => false,
       # :ccache_enabled => true
     )
+
+    # Fix fmt compilation error with Xcode 26.4 (const eval broken in Apple Clang 17+)
+    installer.pods_project.targets.each do |target|
+      if target.name == 'fmt'
+        target.build_configurations.each do |config|
+          config.build_settings['CLANG_CXX_LANGUAGE_STANDARD'] = 'c++17'
+        end
+      end
+    end
   end
 end

FabricExample/ios/Podfile.lock

@@ -3190,6 +3190,6 @@ SPEC CHECKSUMS:
   SocketRocket: d4aabe649be1e368d1318fdf28a022d714d65748
   Yoga: 922d794dce2af9c437f864bf4093abfa7a131adb
 
-PODFILE CHECKSUM: f46c4ff801235007081bd301b6e8daff54c0c492
+PODFILE CHECKSUM: d45f7cf34858c180261cf0d1bee48426d1242c00
 
 COCOAPODS: 1.15.2

example/ios/Podfile

@@ -35,5 +35,14 @@ target 'KeyboardControllerExample' do
       :mac_catalyst_enabled => false,
       # :ccache_enabled => true
     )
+
+    # Fix fmt compilation error with Xcode 26.4 (const eval broken in Apple Clang 17+)
+    installer.pods_project.targets.each do |target|
+      if target.name == 'fmt'
+        target.build_configurations.each do |config|
+          config.build_settings['CLANG_CXX_LANGUAGE_STANDARD'] = 'c++17'
+        end
+      end
+    end
   end
 end

example/ios/Podfile.lock

@@ -3017,6 +3017,6 @@ SPEC CHECKSUMS:
   SocketRocket: d4aabe649be1e368d1318fdf28a022d714d65748
   Yoga: 922d794dce2af9c437f864bf4093abfa7a131adb
 
-PODFILE CHECKSUM: c51a5e2124b01c5794c41f1f13ee16704466637a
+PODFILE CHECKSUM: 6a517affee16b03f1ddaf7ff04b3a32770880334
 
 COCOAPODS: 1.15.2