Fix race condition in generating header

Use a define to create the file in one go.
Fixes #1853

diff --git a/pdns/Makefile.am b/pdns/Makefile.am
index 0b0ee94c5f0b644b3547442a1aaaabd9d430343a..eef73aa9281e3ce29dffeb1521505d748ba4aaee 100644 (file)
--- a/pdns/Makefile.am
+++ b/pdns/Makefile.am
@@ -976,10 +976,16 @@ pubsuffix.cc: $(srcdir)/effective_tld_names.dat
 
 .PHONY: version_generated.h
 version_generated.h:
-       @echo '#ifndef VERSION_GENERATED_H' > $@
-       @echo '#define VERSION_GENERATED_H' >> $@
-       @echo '#define PDNS_VERSION "$(pdns_version)"' >> $@
-       @echo '#define DIST_HOST "$(dist_host)"' >> $@
-       @echo '#define BUILD_DATE "$(build_date)"' >> $@
-       @echo '#define BUILD_HOST "$(build_host)"' >> $@
-       @echo '#endif //!VERSION_GENERATED_H' >> $@
+       @echo "$$create_version_generated_h" > $@
+
+define create_version_generated_h
+#ifndef VERSION_GENERATED_H
+#define VERSION_GENERATED_H
+#define PDNS_VERSION "$(pdns_version)"
+#define DIST_HOST "$(dist_host)"
+#define BUILD_DATE "$(build_date)"
+#define BUILD_HOST "$(build_host)"
+#endif //!VERSION_GENERATED_H
+endef
+
+export create_version_generated_h