Revert "tools/build: Unbreak bmake bootstrap on Linux"

Now that make.py no longer has the described hack on Linux we can drop
this ugly workaround.

This reverts commit fba998a3d8.

tools/build/cross-build/include/common/sys/types.h

@@ -69,15 +69,7 @@ struct cap_rights;
 
 typedef struct cap_rights cap_rights_t;
 
-/*
- * make.py uses these headers during the bmake bootstrap on Linux only, at
- * which point sys/bitcount.h won't yet exist, so don't include it there.
- *
- * TODO: Untangle this mess.
- */
-#if __has_include(<sys/bitcount.h>)
 /* Needed for bitstring */
 #include <sys/bitcount.h>
-#endif
 
 #endif