build: qemu-ga: add 'qemu-ga' build target for w32

Currently POSIX builds rely on 'qemu-ga' target to do qga-only
distributable build. On w32, as with most standalone binary targets,
we rely on 'qemu-ga.exe' target.

Unlike with POSIX, qemu-ga for w32 has a number of related targets
such as VSS DLL and MSI package. We can do the full distributable
qga-only build on w32 with:

  make qemu-ga.exe

or:

  make msi

To make that work, we tie VSS dependencies onto qemu-ga.exe.
However, in reality the DLL isn't part of the binary, so we use a
filter to pull them out of the LINK recipe, which attempts to link
against prereqs for binary targets. Additionally, it could be argued
that VSS is a separate distributable, and shouldn't be implied by
qemu-ga.exe binary target.

To avoid this, we can tie the VSS dependencies only to the 'msi'
target, but that would make it impossible to do a qga-only build of
the w32 distributable without building the 'msi' package, which was
supported in the past.

An alternative approach is to add a new target to build the whole
distributable. w32 allows us to use the same build target we use
on POSIX, 'qemu-ga', since the current binary-only target on w32
is 'qemu-ga.exe'.

To further simplify the build, we also make 'qemu-ga' build the MSI
package if the appropriate ./configure options are set, making the
full qga-only build the same on both POSIX and w32: `make qemu-ga`

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

Makefile

@@ -298,18 +298,15 @@ $(qapi-modules) $(SRC_PATH)/scripts/qapi-introspect.py $(qapi-py)
 QGALIB_GEN=$(addprefix qga/qapi-generated/, qga-qapi-types.h qga-qapi-visit.h qga-qmp-commands.h)
 $(qga-obj-y) qemu-ga.o: $(QGALIB_GEN)
 
-# we require QGA_VSS_PROVIDER files to be built alongside qemu-ga
-# executable since they are shipped together, but we don't want to actually
-# link against them
-qemu-ga$(EXESUF): $(qga-obj-y) libqemuutil.a libqemustub.a $(QGA_VSS_PROVIDER)
-	$(call LINK, $(filter-out $(QGA_VSS_PROVIDER), $^))
+qemu-ga$(EXESUF): $(qga-obj-y) libqemuutil.a libqemustub.a
+	$(call LINK, $^)
 
 ifdef QEMU_GA_MSI_ENABLED
 QEMU_GA_MSI=qemu-ga-$(ARCH).msi
 
 msi: $(QEMU_GA_MSI)
 
-$(QEMU_GA_MSI): qemu-ga.exe
+$(QEMU_GA_MSI): qemu-ga.exe $(QGA_VSS_PROVIDER)
 
 $(QEMU_GA_MSI): config-host.mak
 
@@ -321,6 +318,11 @@ msi:
 	@echo "MSI build not configured or dependency resolution failed (reconfigure with --enable-guest-agent-msi option)"
 endif
 
+ifneq ($(EXESUF),)
+.PHONY: qemu-ga
+qemu-ga: qemu-ga$(EXESUF) $(QGA_VSS_PROVIDER) $(QEMU_GA_MSI)
+endif
+
 clean:
 # avoid old build problems by removing potentially incorrect old files
 	rm -f config.mak op-i386.h opc-i386.h gen-op-i386.h op-arm.h opc-arm.h gen-op-arm.h

configure

@@ -4437,7 +4437,7 @@ fi
 
 if [ "$guest_agent" != "no" ]; then
   if [ "$linux" = "yes" -o "$bsd" = "yes" -o "$solaris" = "yes" -o "$mingw32" = "yes" ] ; then
-      tools="qemu-ga\$(EXESUF) $tools"
+      tools="qemu-ga $tools"
       guest_agent=yes
   elif [ "$guest_agent" != yes ]; then
       guest_agent=no