cogl/tests: Use tmp file to dump test results

When running installed tests, the working directory for Cogl
tests is /usr/libexec/installed-tests/mutter-cogl-4/conform,
which isn't writable by normal users.

To avoid the adding stray hidden files to the current directory,
adapt the runner script to fallback to $(mktemp) - which is
available on all platform we care about - and avoid adding
hidden files everywhere.

cogl/tests/run-tests.sh

@@ -21,6 +21,8 @@ shift
 
 set +m
 
+LOG=$(mktemp)
+
 trap "" ERR
 trap "" SIGABRT
 trap "" SIGFPE
@@ -65,17 +67,17 @@ get_status()
 
 run_test()
 {
-  $("$TEST_BINARY" "$1" &>.log)
+  $("$TEST_BINARY" "$1" &> "$LOG")
   TMP=$?
   var_name=$2_result
   eval "$var_name=$TMP"
-  if grep -q "$MISSING_FEATURE" .log; then
+  if grep -q "$MISSING_FEATURE" "$LOG"; then
     if test "$TMP" -ne 0; then
       eval "$var_name=500"
     else
       eval "$var_name=400"
     fi
-  elif grep -q "$KNOWN_FAILURE" .log; then
+  elif grep -q "$KNOWN_FAILURE" "$LOG"; then
     if test $TMP -ne 0; then
       eval "$var_name=300"
     else
@@ -156,4 +158,6 @@ do
   echo ""
 done
 
+rm "$LOG"
+
 exit "$EXIT"