build-release-tarball: Fix shellcheck warnings.
build-release-tarball: Fix shellcheck warnings.

In tools/build-release-tarball line 50:
for i in `cat "$TMPDIR/$prefix/tools/release-tarball-exclude.txt"`; do
         ^-- SC2013: To read lines rather than words, pipe/redirect to a 'while read' loop.
         ^-- SC2006: Use $(..) instead of legacy `..`.

In tools/build-release-tarball line 51:
    rm -r --interactive=never "$TMPDIR/$prefix/$i";
                              ^-- SC2115: Use "${var:?}" to ensure this never expands to / .

In tools/build-release-tarball line 97:
    echo; echo -ne "\033[33mRunning update-prod-static failed. "
                    ^-- SC1117: Backslash is literal in "\0". Prefer explicit escaping: "\\0".

In tools/build-release-tarball line 98:
    echo -e "Check $TMPDIR/update-prod-static.log for more information.\033[0m"
                                                                       ^-- SC1117: Backslash is literal in "\0". Prefer explicit escaping: "\\0".

Signed-off-by: Anders Kaseorg <087231934ba8fcf78bc142ce37d193b895ac03c4@mit.edu>

jackrzhang/zulip,jackrzhang/zulip,brainwane/zulip,rishig/zulip,rishig/zulip,shubhamdhama/zulip,punchagan/zulip,rht/zulip,dhcrzf/zulip,brainwane/zulip,kou/zulip,brainwane/zulip,shubhamdhama/zulip,timabbott/zulip,kou/zulip,timabbott/zulip,timabbott/zulip,andersk/zulip,tommyip/zulip,dhcrzf/zulip,tommyip/zulip,dhcrzf/zulip,punchagan/zulip,brainwane/zulip,jackrzhang/zulip,synicalsyntax/zulip,showell/zulip,synicalsyntax/zulip,andersk/zulip,rht/zulip,kou/zulip,timabbott/zulip,eeshangarg/zulip,rishig/zulip,shubhamdhama/zulip,shubhamdhama/zulip,hackerkid/zulip,rht/zulip,andersk/zulip,punchagan/zulip,dhcrzf/zulip,zulip/zulip,jackrzhang/zulip,hackerkid/zulip,zulip/zulip,zulip/zulip,timabbott/zulip,rht/zulip,zulip/zulip,showell/zulip,andersk/zulip,timabbott/zulip,kou/zulip,eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,kou/zulip,brainwane/zulip,punchagan/zulip,brainwane/zulip,eeshangarg/zulip,rht/zulip,rishig/zulip,hackerkid/zulip,dhcrzf/zulip,jackrzhang/zulip,shubhamdhama/zulip,hackerkid/zulip,rishig/zulip,kou/zulip,timabbott/zulip,showell/zulip,kou/zulip,hackerkid/zulip,hackerkid/zulip,synicalsyntax/zulip,punchagan/zulip,eeshangarg/zulip,jackrzhang/zulip,andersk/zulip,punchagan/zulip,tommyip/zulip,synicalsyntax/zulip,showell/zulip,tommyip/zulip,showell/zulip,dhcrzf/zulip,synicalsyntax/zulip,jackrzhang/zulip,shubhamdhama/zulip,synicalsyntax/zulip,brainwane/zulip,andersk/zulip,dhcrzf/zulip,eeshangarg/zulip,andersk/zulip,zulip/zulip,tommyip/zulip,zulip/zulip,hackerkid/zulip,tommyip/zulip,rht/zulip,rishig/zulip,punchagan/zulip,synicalsyntax/zulip,tommyip/zulip,eeshangarg/zulip,rht/zulip,rishig/zulip,shubhamdhama/zulip,showell/zulip