malloc.h does not exist on macOS. The same functionality is
already provided by stdlib.h, so there's no need for it.
Patch stolen from:
https://github.com/sjackman/homebrew-science-deprecated/blob/master/dsdp.rb

diff --git a/src/sys/dsdploginfo.c b/src/sys/dsdploginfo.c
index 9313549..cee4f93 100644
--- a/src/sys/dsdploginfo.c
+++ b/src/sys/dsdploginfo.c
@@ -6,7 +6,6 @@
 #include <stdarg.h>
 #include <sys/types.h>
 #include <stdlib.h>
-#include <malloc.h>
 #include "dsdpsys.h"
 #include "dsdpbasictypes.h"