libgpiod: ptest: redirect stderr to stdout for test executables

Catch2 (used by the C++ tests) prints its output to stderr instead of
stdout. Redirect stderr to stdout for all test executables.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-support/libgpiod/files/run-ptest

@@ -7,7 +7,7 @@ cd $ptestdir/tests
 
 for testbin in $testbins; do
 	if test -e ./$testbin; then
-		./$testbin > ./$testbin.out
+		./$testbin > ./$testbin.out 2>&1
 		if [ $? -ne 0 ]; then
 			echo "FAIL: $testbin"
 		else