install-shfmt: Add aarch64 support.
install-shfmt: Add aarch64 support.

This fixes a problem provisioning on an ARM64 computer. Tested by
running on M1 Mac.

Fixes part of #18614

zulip/zulip,punchagan/zulip,hackerkid/zulip,zulip/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,kou/zulip,andersk/zulip,andersk/zulip,hackerkid/zulip,kou/zulip,kou/zulip,kou/zulip,rht/zulip,rht/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,eeshangarg/zulip,punchagan/zulip,eeshangarg/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,eeshangarg/zulip,hackerkid/zulip,andersk/zulip,punchagan/zulip,kou/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,zulip/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,zulip/zulip