fix: use signal backend on android #587

Job	Run time
msrv (ubuntu-latest, 1.63)	31s
clippy	9s
msrv (windows-latest, 1.63)	51s
security_audit	6s
fmt	4s
test-android (nightly, aarch64-linux-android)	1m 26s
test (ubuntu-latest, nightly)	30s
test-android (beta, aarch64-linux-android)	1m 26s
test (ubuntu-latest, beta)	28s
test-android (stable, aarch64-linux-android)	1m 57s
test (ubuntu-latest, stable)	23s
test (windows-latest, nightly)	1m 2s
test (windows-latest, beta)	55s
test (windows-latest, stable)	1m 33s
test (macos-latest, nightly)	26s
test (macos-latest, beta)	26s
test (macos-latest, stable)	19s
	12m 32s

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