OpenBSD/macppc is not Mac OS, we don't ship Gestalt.

Index: libfastmint.c
--- libfastmint.c.orig
+++ libfastmint.c
@@ -6,7 +6,7 @@
 #include <CoreServices/CoreServices.h>
 #endif
 
-#if defined(__POWERPC__) && !defined(__MACH__) && !defined(__UNIX__) && !defined(__CARBON__)
+#if defined(__POWERPC__) && !defined(__MACH__) && !defined(__unix__) && !defined(__CARBON__)
 #include <Gestalt.h>
 #endif