fix: use signal backend on android #584

Job	Run time
msrv (ubuntu-latest, 1.63)	26s
fmt	4s
msrv (windows-latest, 1.63)	44s
security_audit	5s
clippy	14s
test (ubuntu-latest, nightly)	31s
test-android (nightly, aarch64-linux-android)	1m 26s
test (ubuntu-latest, beta)	28s
test-android (beta, aarch64-linux-android)	1m 21s
test (ubuntu-latest, stable)	22s
test-android (stable, aarch64-linux-android)	1m 58s
test (windows-latest, nightly)	58s
test (windows-latest, beta)	55s
test (windows-latest, stable)	1m 42s
test (macos-latest, nightly)	24s
test (macos-latest, beta)	26s
test (macos-latest, stable)	21s
	12m 25s

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