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 <bjorn@mork.no>
Link: https://github.com/openwrt/openwrt/pull/20127
Signed-off-by: Robert Marko <robimarko@gmail.com>

rules.mk

@@ -514,9 +514,9 @@ ext=$(word $(words $(subst ., ,$(1))),$(subst ., ,$(1)))
 ##
 define commitcount
 $(shell \
-  if git log -1 >/dev/null 2>/dev/null; then \
+  if git log -1 --no-show-signature >/dev/null 2>/dev/null; then \
     if [ -n "$(1)" ]; then \
-      last_bump="$$(git log --pretty=format:'%h %s' . | \
+      last_bump="$$(git log --no-show-signature --pretty=format:'%h %s' . | \
         grep -m 1 -e ': [uU]pdate to ' -e ': [bB]ump to ' | \
         cut -f 1 -d ' ')"; \
     fi; \