don't run the clean target when building all as we run into parallel races:
 - memtest kicks off building of a bunch of .o files
 - clean runs in parallel which runs `rm` and deletes some of the new .o
 - memtest goes to link and fails because objects are missing

--- a/Makefile
+++ b/Makefile
@@ -19,7 +19,7 @@
 OBJS= head.o reloc.o main.o test.o init.o lib.o patn.o screen_buffer.o \
       config.o memsize.o error.o smp.o cpuid.o vmem.o random.o
 
-all: clean memtest.bin memtest
+all: memtest.bin memtest
 
 # Link it statically once so I know I don't have undefined
 # symbols and then link it dynamically so I have full