Avoid parallel invocation of git for ioemu-remote.

The stubdom and tools directories both run `make ioemu-dir-find' in
tools.  In a parallel build, both these invocations can run
concurrently because we're doing recursive make.

This change fixes this problem by adding a suitable dependencies in
the top-level Makefile for the recursion into tools/ and stubdom/,
ensuring that the git fetch happens once, first.

The bug was introduced in 18472/18474.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

Makefile

@@ -64,7 +64,7 @@ install-xen:
 	$(MAKE) -C xen install
 
 .PHONY: install-tools
-install-tools:
+install-tools: tools/ioemu-dir
 	$(MAKE) -C tools install
 
 .PHONY: install-kernels
@@ -72,12 +72,15 @@ install-kernels:
 	for i in $(XKERNELS) ; do $(MAKE) $$i-install || exit 1; done
 
 .PHONY: install-stubdom
-install-stubdom:
+install-stubdom: tools/ioemu-dir
 	$(MAKE) -C stubdom install
 ifeq (x86_64,$(XEN_TARGET_ARCH))
 	XEN_TARGET_ARCH=x86_32 $(MAKE) -C stubdom install-grub
 endif
 
+tools/ioemu-dir:
+	make -C tools ioemu-dir-find
+
 .PHONY: install-docs
 install-docs:
 	sh ./docs/check_pkgs && $(MAKE) -C docs install || true