8004229: build-infra: Umbrella for switch of default "make" to new makefiles

Reviewed-by: erikj, tbell
diff --git a/Makefile b/Makefile
index 79c159e..f9162f0 100644
--- a/Makefile
+++ b/Makefile
@@ -26,6 +26,11 @@
 # If NEWBUILD is defined, use the new build-infra Makefiles and configure.
 #     See NewMakefile.gmk for more information.
 
+# If not specified, select what the default build is
+ifndef NEWBUILD
+  NEWBUILD=true
+endif
+
 ifeq ($(NEWBUILD),true)
 
   # The new top level Makefile