Update fast_float to v6.1.5 (#5167)

packages/f/fast_float/xmake.lua

@@ -16,6 +16,7 @@ package("fast_float")
     add_versions("v6.1.1", "10159a4a58ba95fe9389c3c97fe7de9a543622aa0dcc12dd9356d755e9a94cb4")
     add_versions("v6.1.3", "7dd99cc2ff44e07dc2a42bed0c6b8c4a8ee4e3b1c330f77073b6cfdb48724c8e")
     add_versions("v6.1.4", "12cb6d250824160ca16bcb9d51f0ca7693d0d10cb444f34f1093bc02acfce704")
+    add_versions("v6.1.5", "597126ff5edc3ee59d502c210ded229401a30dafecb96a513135e9719fcad55f")
 
     if is_plat("wasm") then
         add_patches("v3.4.0", path.join(os.scriptdir(), "patches", "emscripten_fix.patch"), "482705431f67e6f0a375ed7bfe87d6856e7d13f071db6157e1d5659834b0eb50")