gitignore: ignore build signatures (ethereum#30346)

Ignore files are generated during signing of download-binaries, which 'dirty' the vcs for subsequent builds.

Author: holiman

.gitignore

@@ -30,6 +30,11 @@ build/_vendor/pkg
 
 # used by the build/ci.go archive + upload tool
 /geth*.tar.gz
+/geth*.tar.gz.sig
+/geth*.tar.gz.asc
+/geth*.zip.sig
+/geth*.zip.asc
+
 
 # travis
 profile.tmp