Speed up parallel builds

- make should be $(MAKE)
 - add + in front of rules spawning long-lasted make process in a
subshell. (This would not be needed with $(MAKE) -C .. target, but our
makefiles do not handle that because they use $(PWD))
 - split the main 'all' rule as all 4 targets are independant
 - fix dependencies where appropriate for parallelism

Extra, not speed-related changes:
 - remove some double-colon for targets as they do not need it

This cuts build time from 5s to 1.5s on a laptop with -j4, and more
importantly from 85s to 35s on a KNL node.
As a bonus, the fixed dependencies removes the need to clean before
rebuilding all the time. Probably.

Makefile.in

@@ -4,13 +4,21 @@ INCDIR =  @INCDIR@
 ETCDIR = @ETCDIR@
 MANDIR = @MANDIR@
 
-all::
-	@(cd executer/kernel/mcctrl; make modules)
-	@(cd executer/kernel/mcoverlayfs; make modules)
-	@(cd executer/user; make)
-	@case "$(TARGET)" in \
+all: executer-mcctrl executer-mcoverlayfs executer-user mckernel
+
+executer-mcctrl:
+	+@(cd executer/kernel/mcctrl; $(MAKE) modules)
+
+executer-mcoverlayfs:
+	+@(cd executer/kernel/mcoverlayfs; $(MAKE) modules)
+
+executer-user:
+	+@(cd executer/user; $(MAKE))
+
+mckernel:
+	+@case "$(TARGET)" in \
 	    attached-mic | builtin-x86 | builtin-mic | smp-x86 | smp-arm64) \
-		(cd kernel; make) \
+		(cd kernel; $(MAKE)) \
 		;; \
 	    *) \
 		echo "unknown target $(TARGET)" >&2 \
@@ -18,13 +26,13 @@ all::
 		;; \
 	esac
 
-install::
-	@(cd executer/kernel/mcctrl; make install)
-	@(cd executer/kernel/mcoverlayfs; make install)
-	@(cd executer/user; make install)
+install:
+	@(cd executer/kernel/mcctrl; $(MAKE) install)
+	@(cd executer/kernel/mcoverlayfs; $(MAKE) install)
+	@(cd executer/user; $(MAKE) install)
 	@case "$(TARGET)" in \
 	    attached-mic | builtin-x86 | builtin-mic | smp-x86 | smp-arm64) \
-		(cd kernel; make install) \
+		(cd kernel; $(MAKE) install) \
 		;; \
 	    *) \
 		echo "unknown target $(TARGET)" >&2 \
@@ -67,13 +75,13 @@ install::
 		;; \
 	esac
 
-clean::
-	@(cd executer/kernel/mcctrl; make clean)
-	@(cd executer/kernel/mcoverlayfs; make clean)
-	@(cd executer/user; make clean)
+clean:
+	@(cd executer/kernel/mcctrl; $(MAKE) clean)
+	@(cd executer/kernel/mcoverlayfs; $(MAKE) clean)
+	@(cd executer/user; $(MAKE) clean)
 	@case "$(TARGET)" in \
 	    attached-mic | builtin-x86 | builtin-mic | smp-x86 | smp-arm64) \
-		(cd kernel; make clean) \
+		(cd kernel; $(MAKE) clean) \
 		;; \
 	    *) \
 		echo "unknown target $(TARGET)" >&2 \

executer/kernel/mcoverlayfs/Makefile.in

@@ -33,7 +33,7 @@ endif
 
 modules:
 ifneq ($(BUILD_MODULE),none)
-	@(cd $(BUILD_MODULE); make modules)
+	+@(cd $(BUILD_MODULE); make modules)
 endif
 
 clean:

executer/user/Makefile.in

@@ -53,7 +53,7 @@ libsched_yield: libsched_yield.c
 	$(CC) -shared -fPIC -Wl,-soname,sched_yield.so.1 -o libsched_yield.so.1.0.0 $^ -lc -ldl
 
 libmcexec.a::
-	(cd arch/${ARCH}; make)
+	+(cd arch/${ARCH}; $(MAKE))
 
 libqlmpi.so: qlmpilib.c
 	$(MCC) $(CFLAGS) $(LDFLAGS) -shared -fPIC -o $@ $<
@@ -77,13 +77,13 @@ ql_talker: ql_talker.o
 	$(CC) $^ $(CFLAGS) -o $@
 
 clean::
-	(cd arch/${ARCH}; make clean)
+	(cd arch/${ARCH}; $(MAKE) clean)
 	$(RM) $(TARGET) *.o
 
 .PHONY: all clean install
 
 install::
-	(cd arch/${ARCH}; make install)
+	(cd arch/${ARCH}; $(MAKE) install)
 	mkdir -p -m 755 $(BINDIR)
 	install -m 755 mcexec $(BINDIR)
 	mkdir -p -m 755 $(MCKERNEL_LIBDIR)

kernel/Makefile.build.in

@@ -65,8 +65,8 @@ Makefile.dep:
 
 $(IHKOBJ): FORCE
 	@mkdir -p $(dir $(IHKOBJ))
-	$(call echo_cmd,BUILD IHK,$(TARGET))$(submake) -C $(IHKBASE) $(SUBCMD_OPTS) prepare
-	$(call echo_cmd,BUILD IHK,$(TARGET))$(submake) -C $(IHKBASE) $(SUBCMD_OPTS)
+	+$(call echo_cmd,BUILD IHK,$(TARGET))$(submake) -C $(IHKBASE) $(SUBCMD_OPTS) prepare
+	+$(call echo_cmd,BUILD IHK,$(TARGET))$(submake) -C $(IHKBASE) $(SUBCMD_OPTS)
 
 %.o: $(SRC)/%.c
 	$(cc_cmd)

kernel/Makefile.in

@@ -26,9 +26,9 @@ all: $(O) $(KERNELS)
 $(O):
 	mkdir -p $(O)
 
-%/kernel.img: %/Makefile
+%/kernel.img: %/Makefile $(KERNELS)
 	@echo 'Building for' $(dir $@)
-	@make --no-print-directory -C $(dir $@) $(SUBCMD_OPTS)
+	+@make --no-print-directory -C $(dir $@) $(SUBCMD_OPTS)
 
 %/Makefile: Makefile.build FORCE
 	@mkdir -p $(dir $@)