build-sys: introduce install-prog macro to install&strip binaries and use it

Use common rule (macro) to install and strip binaries, and use
it in all places where we install binaries, instead of fixing
bugs like 1319493 in every place.
(This fixes https://bugs.launchpad.net/bugs/1319493)

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/Makefile b/Makefile
index 7d0c8ec..145adb6 100644
--- a/Makefile
+++ b/Makefile
@@ -385,12 +385,8 @@
 
 install: all $(if $(BUILD_DOCS),install-doc) install-sysconfig \
 install-datadir install-localstatedir
-	$(INSTALL_DIR) "$(DESTDIR)$(bindir)"
 ifneq ($(TOOLS),)
-	$(INSTALL_PROG) $(TOOLS) "$(DESTDIR)$(bindir)"
-ifneq ($(STRIP),)
-	$(STRIP) $(TOOLS:%="$(DESTDIR)$(bindir)/%")
-endif
+	$(call install-prog,$(TOOLS),$(DESTDIR)$(bindir))
 endif
 ifneq ($(CONFIG_MODULES),)
 	$(INSTALL_DIR) "$(DESTDIR)$(qemu_moddir)"
@@ -401,11 +397,7 @@
 	done
 endif
 ifneq ($(HELPERS-y),)
-	$(INSTALL_DIR) "$(DESTDIR)$(libexecdir)"
-	$(INSTALL_PROG) $(HELPERS-y) "$(DESTDIR)$(libexecdir)"
-ifneq ($(STRIP),)
-	$(STRIP) $(HELPERS-y:%="$(DESTDIR)$(libexecdir)/%")
-endif
+	$(call install-prog,$(HELPERS-y),$(DESTDIR)$(libexecdir))
 endif
 ifneq ($(BLOBS),)
 	set -e; for x in $(BLOBS); do \