Bump fmt to 12.1.0 to fix xcode 26.4 (#56099)

Summary:
Follow-up to
- #47033
- #50431

TODO
- [x] bump packages/react-native/third-party-podspecs/fmt.podspec
- [x] bump scripts/releases/ios-prebuild/configuration.js
- [x] packages/react-native/third-party-podspecs/RCT-Folly.podspec
- [x] packages/react-native/gradle/libs.versions.toml
- [x] packages/rn-tester/Podfile.lock
  - rn-rester (main) ios not building on Xcode 26.3, CI currently only supports Xcode 16
  - i cannot downgrade macos26.4b4 locally to macos15 to install Xcode16.4 and bump pods this way
  - so on Xcode 26.3 i've attempted to bump only fmt minimally, ignoring remaining RN 0.86 hashes

Ref: https://github.com/search?q=repo%3Afacebook%2Freact-native+%2211.0.2%22&type=code

however unable to test rn-tester, ios doesn't seem to build on Xcode 26.3 let alone 26.4b
not tested previous versions of Xcode
not tested prior branches/tags to main

rn-tester CI is passing on old macos-15 Xcode 16.4.0 only, ideally this should be extended to stable macos lts and Xcode 26.3 stable first

separate follow-ups to this minimal fmt bump
- bump CI macos-15 xcode 16.1-4 to macos-26 xcode 26.0-3
- bump rn-tester Podfile.lock from RN 0.82 to 0.86 main (aka nightly)
- bump folly to 2025.11.03.00
- bump folly to 2026.03.09.00

Resolve: #55601

[General][Changed] Bump fmt to 12.1.0 to fix Xcode 26.4

Pull Request resolved: #56099

Test Plan: RNTester

Reviewed By: alanleedev

Differential Revision: D97358194

Pulled By: cipolleschi

fbshipit-source-id: 3eb578a99a310e3eb77433692bf35502d0d78d24

Author: leotm

packages/react-native/gradle/libs.versions.toml

@@ -44,7 +44,7 @@ yoga-proguard-annotations = "1.19.0"
 boost="1_83_0"
 doubleconversion="1.1.6"
 fastFloat="8.0.0"
-fmt="11.0.2"
+fmt="12.1.0"
 folly="2024.11.18.00"
 glog="0.3.5"
 gflags="2.2.0"

packages/react-native/third-party-podspecs/RCT-Folly.podspec

@@ -25,7 +25,7 @@ Pod::Spec.new do |spec|
   spec.dependency "DoubleConversion"
   spec.dependency "glog"
   spec.dependency "fast_float", "8.0.0"
-  spec.dependency "fmt", "11.0.2"
+  spec.dependency "fmt", "12.1.0"
   spec.compiler_flags = '-Wno-documentation -faligned-new'
   spec.source_files = 'folly/String.cpp',
                       'folly/Conv.cpp',

packages/react-native/third-party-podspecs/fmt.podspec

@@ -8,14 +8,14 @@ fmt_git_url = fmt_config[:git]
 
 Pod::Spec.new do |spec|
   spec.name = "fmt"
-  spec.version = "11.0.2"
+  spec.version = "12.1.0"
   spec.license = { :type => "MIT" }
   spec.homepage = "https://github.com/fmtlib/fmt"
   spec.summary = "{fmt} is an open-source formatting library for C++. It can be used as a safe and fast alternative to (s)printf and iostreams."
   spec.authors = "The fmt contributors"
   spec.source = {
     :git => fmt_git_url,
-    :tag => "11.0.2"
+    :tag => "12.1.0"
   }
   spec.pod_target_xcconfig = {
     "CLANG_CXX_LANGUAGE_STANDARD" => rct_cxx_language_standard(),

scripts/releases/ios-prebuild/configuration.js

@@ -80,9 +80,9 @@ const dependencies /*: $ReadOnlyArray<Dependency> */ = [
   },
   {
     name: 'fmt',
-    version: '11.0.2',
+    version: '12.1.0',
     url: new URL(
-      'https://github.com/fmtlib/fmt/archive/refs/tags/11.0.2.tar.gz',
+      'https://github.com/fmtlib/fmt/archive/refs/tags/12.1.0.tar.gz',
     ),
     files: {
       sources: ['src/format.cc', 'include/fmt/*.h'],