[Windows] Use 'ninja' instead of 'ninja.exe' (#39326)

diff --git a/tools/gn b/tools/gn
index 1132d28..9215fd6 100755
--- a/tools/gn
+++ b/tools/gn
@@ -1056,6 +1056,7 @@
     elif sys.platform.startswith('win'):
       # On Windows, generate a Visual Studio project.
       command.append('--ide=vs')
+      command.append('--ninja-executable=ninja')
 
   command.append('--export-compile-commands=default')