[LibOS] native/Makefile, benchmark/Makefile: Use implicit pattern rules

LibOS/shim/test/benchmark/Makefile

@@ -2,7 +2,7 @@ c_executables = $(patsubst %.c,%,$(wildcard *.c))
 cxx_executables = $(patsubst %.cpp,%,$(wildcard *.cpp))
 
 exec_target = $(c_executables) $(cxx_executables)
-target = manifest
+target = $(exec_target) manifest
 
 include ../../../../Scripts/Makefile.Test
 
@@ -15,10 +15,10 @@ LDLIBS-rpc_latency += -llibos
 LDLIBS-rpc_latency2 += -llibos
 LDLIBS-test_start += -lm
 
-$(c_executables): %: %.c
+%: %.c
 	$(call cmd,csingle)
 
-$(cxx_executables): %: %.cpp
+%: %.cpp
 	$(call cmd,cxxsingle)
 else
 .IGNORE: $(c_executables) $(cxx_executables)

LibOS/shim/test/native/Makefile

@@ -23,10 +23,10 @@ LDLIBS-start += -lpthread -lm
 LDLIBS-sync += -lpthread
 LDLIBS-test_start_pthread_m += -lm
 
-$(c_executables): %: %.c
+%: %.c
 	$(call cmd,csingle)
 
-$(cxx_executables): %: %.cpp
+%: %.cpp
 	$(call cmd,cxxsingle)
 
 ifeq ($(filter %clean,$(MAKECMDGOALS)),)