gitian-build.sh: fix signProg being recognized as two parameters
gitian-build.sh: fix signProg being recognized as two parameters

dagurval/bitcoinxt,dagurval/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt