Remove set -e and print error messages in BTF general tests.

Before:
    $ sudo /tmp/perf test btf -vv
    108: perf trace BTF general tests:
    108: perf trace BTF general tests                                    : Running
    --- start ---
    test child forked, pid 889299
    Checking if vmlinux BTF exists
    Testing perf trace's string augmentation
    String augmentation test failed
    ---- end(-1) ----
    108: perf trace BTF general tests                                    : FAILED!

After:
    $ sudo /tmp/perf test btf -vv
    108: perf trace BTF general tests:
    108: perf trace BTF general tests                                    : Running
    --- start ---
    test child forked, pid 886551
    Checking if vmlinux BTF exists
    Testing perf trace's string augmentation
    String augmentation test failed, output:
    :886566/886566 renameat2(CWD, "/tmp/file1_RcMa", CWD, "/tmp/file2_RcMa", NOREPLACE) = 0---- end(-1) ----
    108: perf trace BTF general tests                                    : FAILED!

Signed-off-by: Howard Chu <howardchu95@gmail.com>
---
 tools/perf/tests/shell/trace_btf_general.sh | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/tools/perf/tests/shell/trace_btf_general.sh b/tools/perf/tests/shell/trace_btf_general.sh
index a25d8744695e..5fa50d815203 100755
--- a/tools/perf/tests/shell/trace_btf_general.sh
+++ b/tools/perf/tests/shell/trace_btf_general.sh
@@ -3,7 +3,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
 err=0
-set -e
 
 # shellcheck source=lib/probe.sh
 . "$(dirname $0)"/lib/probe.sh
@@ -28,10 +27,10 @@ check_vmlinux() {
 
 trace_test_string() {
   echo "Testing perf trace's string augmentation"
-  if ! perf trace -e renameat* --max-events=1 -- mv ${file1} ${file2} 2>&1 | \
-    grep -q -E "^mv/[0-9]+ renameat(2)?\(.*, \"${file1}\", .*, \"${file2}\", .*\) += +[0-9]+$"
+  output="$(perf trace -e renameat* --max-events=1 -- mv ${file1} ${file2} 2>&1)"
+  if ! echo "$output" | grep -q -E "^mv/[0-9]+ renameat(2)?\(.*, \"${file1}\", .*, \"${file2}\", .*\) += +[0-9]+$"
   then
-    echo "String augmentation test failed"
+    printf "String augmentation test failed, output:\n$output\n"
     err=1
   fi
 }
@@ -39,20 +38,20 @@ trace_test_string() {
 trace_test_buffer() {
   echo "Testing perf trace's buffer augmentation"
   # echo will insert a newline (\10) at the end of the buffer
-  if ! perf trace -e write --max-events=1 -- echo "${buffer}" 2>&1 | \
-    grep -q -E "^echo/[0-9]+ write\([0-9]+, ${buffer}.*, [0-9]+\) += +[0-9]+$"
+  output="$(perf trace -e write --max-events=1 -- echo "${buffer}" 2>&1)"
+  if ! echo "$output" | grep -q -E "^echo/[0-9]+ write\([0-9]+, ${buffer}.*, [0-9]+\) += +[0-9]+$"
   then
-    echo "Buffer augmentation test failed"
+    printf "Buffer augmentation test failed, output:\n$output\n"
     err=1
   fi
 }
 
 trace_test_struct_btf() {
   echo "Testing perf trace's struct augmentation"
-  if ! perf trace -e clock_nanosleep --force-btf --max-events=1 -- sleep 1 2>&1 | \
-    grep -q -E "^sleep/[0-9]+ clock_nanosleep\(0, 0, \{1,\}, 0x[0-9a-f]+\) += +[0-9]+$"
+  output="$(perf trace -e clock_nanosleep --force-btf --max-events=1 -- sleep 1 2>&1)"
+  if ! echo "$output" | grep -q -E "^sleep/[0-9]+ clock_nanosleep\(0, 0, \{1,\}, 0x[0-9a-f]+\) += +[0-9]+$"
   then
-    echo "BTF struct augmentation test failed"
+	printf "BTF struct augmentation test failed, output:\n$output\n"
     err=1
   fi
 }
-- 
2.45.2