xfstests: simplify build of preallo_rw_pattern_reader/writer

Instead of having complicated build system hacks just create two
two-line source files defining READ/WRITE and including iopat.c

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

src/Makefile

@@ -51,19 +51,9 @@ LDIRT = $(TARGETS)
 
 default: $(TARGETS) $(SUBDIRS)
 
-PREALLO_TARGETS = preallo_rw_pattern_reader preallo_rw_pattern_writer
-
 include $(BUILDRULES)
 
-preallo_rw_pattern_reader:
-	@echo "    [CC]    $@"
-	$(Q)$(LTLINK) iopat.c -DREAD -o $@ $(CFLAGS) $(LDFLAGS) $(LDLIBS) $(LIBTEST)
-
-preallo_rw_pattern_writer:
-	@echo "    [CC]    $@"
-	$(Q)$(LTLINK) iopat.c -DWRITE -o $@ $(CFLAGS) $(LDFLAGS) $(LDLIBS) $(LIBTEST)
-
-$(filter-out $(PREALLO_TARGETS), $(TARGETS)): $(LIBTEST)
+$(TARGETS): $(LIBTEST)
 	@echo "    [CC]    $@"
 	$(Q)$(LTLINK) $@.c -o $@ $(CFLAGS) $(LDFLAGS) $(LDLIBS) $(LIBTEST)
 

src/preallo_rw_pattern_reader.c

@@ -0,0 +1,2 @@
+#define READ
+#include "iopat.c"

src/preallo_rw_pattern_writer.c

@@ -0,0 +1,2 @@
+#define WRITE
+#include "iopat.c"