Bump NDK to r26b (#8450)

Changes: https://github.com/android/ndk/wiki/Changelog-r26#r26b

NDK r26 failed to update LLVM to v17.0.1 and instead shipped with an
earlier beta build of the v17 toolchain.  r26b fixes this mistake and
updates LLVM to 17.0.2, based on:

  * https://github.com/llvm/llvm-project/commits/c4c5e79dd4b4c78eee7cffd9b0d7394b5bedcf12
  * https://android.googlesource.com/toolchain/llvm-project/+/d9f89f4d16663d5012e5c09495f3b30ece3d2362

build-tools/xaprepare/xaprepare/ConfigAndData/BuildAndroidPlatforms.cs

@@ -5,8 +5,8 @@ namespace Xamarin.Android.Prepare
 {
 	class BuildAndroidPlatforms
 	{
-		public const string AndroidNdkVersion = "26";
-		public const string AndroidNdkPkgRevision = "26.0.10792818";
+		public const string AndroidNdkVersion = "26b";
+		public const string AndroidNdkPkgRevision = "26.1.10909125";
 		public const int NdkMinimumAPI = 21;
 		public const int NdkMinimumAPILegacy32 = 21;