Make bootstrap shell script set ubi to executable #352

Job	Run time
Alpine Linux	2m 5s
FreeBSD-x86_64 with rust stable	54s
Linux-x86_64 with rust stable	2m 18s
Linux-x86_64 (rustls-native-roots) with rust stable	3m 7s
Linux-x86_64 (native-tls) with rust stable	3m 23s
Linux-x86_64 (native-tls-vendored) with rust stable	4m 41s
Linux-aarch64 with rust stable	2m 40s
Linux-arm with rust stable	2m 27s
Linux-i686 with rust stable	2m 3s
Linux-powerpc with rust stable	1m 46s
Linux-powerpc64 with rust stable	2m 39s
Linux-powerpc64le with rust stable	1m 47s
Linux-riscv64 with rust stable	2m 18s
Linux-s390x with rust stable	1m 58s
NetBSD-x86_64 with rust stable	2m 10s
Windows-aarch64 with rust stable	5m 53s
Windows-i686 with rust stable	2m 25s
Windows-x86_64 with rust stable	6m 14s
macOS-x86_64 with rust stable	2m 4s
macOS-aarch64 with rust stable	1m 1s
Linux-x86_64 with rust beta	3m 1s
Linux-x86_64 with rust nightly	3m 3s
	59m 57s

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