Windows: Use osslsigncode from PATH for signing

We were shipping a pre-built version but it only works on specific distros
as it's tightly coupled to openssl. When upgrading from F34 to F35 it started
segfaulting.

We now rely on the version packaged by Fedora which should be installed on the
host, or compiled and installed manually in PATH by users.

build-release.sh

@@ -7,18 +7,18 @@ set -e
 # For signing keystore and password.
 source ./config.sh
 
-can_sign=0
-if [ ! -z "${SIGN_KEYSTORE}" ] && [ ! -z "${SIGN_PASSWORD}" ]; then
-  can_sign=1
+can_sign_windows=0
+if [ ! -z "${SIGN_KEYSTORE}" ] && [ ! -z "${SIGN_PASSWORD}" ] && [[ $(type -P "osslsigncode") ]]; then
+  can_sign_windows=1
 else
-  echo "Disabling binary signing as config.sh does not define the required data."
+  echo "Disabling Windows binary signing as config.sh does not define the required data (SIGN_KEYSTORE, SIGN_PASSWORD), or osslsigncode can't be found in PATH."
 fi
 
 sign_windows() {
-  if [ $can_sign == 0 ]; then
+  if [ $can_sign_windows == 0 ]; then
     return
   fi
-  ./osslsigncode -pkcs12 ${SIGN_KEYSTORE} -pass "${SIGN_PASSWORD}" -n "${SIGN_NAME}" -i "${SIGN_URL}" -t http://timestamp.comodoca.com -in $1 -out $1-signed
+  osslsigncode sign -pkcs12 ${SIGN_KEYSTORE} -pass "${SIGN_PASSWORD}" -n "${SIGN_NAME}" -i "${SIGN_URL}" -t http://timestamp.comodoca.com -in $1 -out $1-signed
   mv $1-signed $1
 }