build: parsing "git log" breaks with gpg signature verification

build: parsing "git log" breaks with gpg signature verification

Parsing "git log" is fragile.  The actual output depends on both global and
local configuration files. Enabling "log.showSignature" makes "git log" prefix
signed commits with multiple lines of gpg verify output, regardless of the
configured log format.

Add "--no-show-signature" to "git log" commands to work around this particular
issue.

Signed-off-by: Bjørn Mork <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20127
Signed-off-by: Robert Marko <[email protected]>