build

Update Rack to 2.4 #1644

Job	Run time
linux-x86_64-debug	7m 31s
linux (aarch64)	6m 32s
headless	8m 52s
linux (armhf)	6m 37s
linux (i386)	6m 10s
lto	8m 24s
macos (universal-10.15)	19m 40s
linux (riscv64)	6m 29s
modaudio (modduo, modduo-static, MODDUO=true)	17m 8s
linux (x86_64)	6m 31s
modaudio (modduox, modduox-static)	17m 37s
plugin-validation	13m 0s
modaudio (moddwarf, moddwarf)	17m 37s
source-tarball	14m 26s
sysdeps	8m 49s
wasm (simd)	10m 30s
windows (win32)	11m 1s
wasm (nosimd)	10m 51s
windows (win64)	11m 22s
	3h 29m 7s

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