perf tests: Remove bash construct from record+zstd_comp_decomp.sh

Commit 463538a383a2 ("perf tests: Fix test 68 zstd compression for
s390") inadvertently removed the -g flag from all platforms rather than
just s390, because the [[ ]] construct fails in sh. Changing to single
brackets restores testing of call graphs and removes the following error
from the output:

$ ./perf test -v 85
85: Zstd perf.data compression/decompression :
--- start ---
test child forked, pid 50643
Collecting compressed record file:
./tests/shell/record+zstd_comp_decomp.sh: 15: [[: not found

Fixes: 463538a383a2 ("perf tests: Fix test 68 zstd compression for s390")
Signed-off-by: James Clark <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Florian Fainelli <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: John Fastabend <[e-mail]>
Cc: KP Singh <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Martin KaFai Lau <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Song Liu <[e-mail]>
Cc: Sumanth Korikkar <[e-mail]>
Cc: Thomas Richter <[e-mail]>
Cc: Yonghong Song <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/record+zstd_comp_decomp.sh

···
 
 collect_z_record() {
 	echo "Collecting compressed record file:"
-	[[ "$(uname -m)" != s390x ]] && gflag='-g'
+	[ "$(uname -m)" != s390x ] && gflag='-g'
 	$perf_tool record -o $trace_file $gflag -z -F 5000 -- \
 		dd count=500 if=/dev/urandom of=/dev/null
 }