Enforce minimum compiler versions

gcc 9.3
clang 10

using unsupported compiler versions will generate an error,
older version might miscompile SF

CI: improves output on failed bench output

closes https://github.com/official-stockfish/Stockfish/pull/6032

No functional change

tests/signature.sh

@@ -2,16 +2,26 @@
 # obtain and optionally verify Bench / signature
 # if no reference is given, the output is deliberately limited to just the signature
 
+STDOUT_FILE=$(mktemp)
+STDERR_FILE=$(mktemp)
+
 error()
 {
   echo "running bench for signature failed on line $1"
+  echo "===== STDOUT ====="
+  cat "$STDOUT_FILE"
+  echo "===== STDERR ====="
+  cat "$STDERR_FILE"
+  rm -f "$STDOUT_FILE" "$STDERR_FILE"
   exit 1
 }
 trap 'error ${LINENO}' ERR
 
 # obtain
+eval "$WINE_PATH ./stockfish bench" > "$STDOUT_FILE" 2> "$STDERR_FILE" || error ${LINENO}
+signature=$(grep "Nodes searched  : " "$STDERR_FILE" | awk '{print $4}')
 
-signature=`eval "$WINE_PATH ./stockfish bench 2>&1" | grep "Nodes searched  : " | awk '{print $4}'`
+rm -f "$STDOUT_FILE" "$STDERR_FILE"
 
 if [ $# -gt 0 ]; then
    # compare to given reference
@@ -28,4 +38,4 @@ if [ $# -gt 0 ]; then
 else
    # just report signature
    echo $signature
-fi
+fi