File kismet-fix-build.patch of Package kismet

diff --git a/Makefile.in b/Makefile.in
index ff15553..d3684be 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -271,9 +271,9 @@ INSTBINS = $(PS) $(DATASOURCE_BINS) $(LOGTOOL_BINS) $(TOOL_BINS)
 
 # Detect date from variables or now
 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 -u)
+	BUILD_DATE = $(shell date -u)
 endif
 
 all:	$(ALL)