FAB-3675 add gotools/build and fix

Murali caught that gotools/build tree wasn't excluded. However,
it also highlighted a bug in the grep, so refactored.

Change-Id: Ie0afa5151a1e48fdfa333e883077287c19bcda4b
Signed-off-by: Christopher Ferris <chrisfer@us.ibm.com>

scripts/check_license.sh

@@ -1,10 +1,11 @@
 #!/bin/bash
 
 echo "Checking Go files for license headers ..."
-missing=`grep -l -L "Apache License" \`find . -name "*.go"\` | grep -v "./vendor" | grep -v "build/docker/gotools" | grep -v ".pb.go" | grep -v "examples/chaincode/go/utxo/consensus/consensus.go"`
-if [ $? -eq 0 ]; then
-   echo "The following files are missing license headers:"
-   echo "$missing"
-   exit 1
+missing=`find . -name "*.go" | grep -v build/ | grep -v vendor/ | grep -v ".pb.go" | grep -v "examples/chaincode/go/utxo/consensus/consensus.go" | xargs grep -l -L "Apache License"`
+if [ -z "$missing" ]; then
+   echo "All go files have license headers"
+   exit 0
 fi
-echo "All go files have license headers"
+echo "The following files are missing license headers:"
+echo "$missing"
+exit 1