File kismet-fix-build.patch of Package kismet

Index: kismet-kismet-2020-12-R3/Makefile.in
===================================================================
--- kismet-kismet-2020-12-R3.orig/Makefile.in
+++ kismet-kismet-2020-12-R3/Makefile.in
@@ -250,9 +250,9 @@ all-with-plugins:
 
 # Autogen the version file
 ifdef SOURCE_DATE_EPOCH
-	BUILD_DATE ?= $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" 2>/dev/null || date -u)
+BUILD_DATE = $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" 2>/dev/null || date -u)
 else
-	BUILD_DATE ?= $(shell date)
+BUILD_DATE = $(shell date)
 endif
 version.c:	FORCE
 	@{ $(GIT) rev-parse --short HEAD 2>/dev/null || echo "non-git-release"; } | awk ' BEGIN {print "#include \"version.h\""} {print "const char *VERSION_GIT_COMMIT = \"" $$0"\";"} END {}' > version.c