Make did not seem to understand the case statment

```
10:59:27 case "ubuntu-20.04" in
10:59:27 /bin/sh: 1: Syntax error: end of file unexpected (expecting ")")
```

Signed-off-by: Lars Erik Wik <lars.erik.wik@northern.tech>

Author: larsewi

deps-packaging/git/debian/rules

@@ -23,14 +23,8 @@ install: build
 	dh_clean -k
 	dh_installdirs
 
-	case "$(OS)-$(OS_VERSION)" in
-		ubuntu-16*)
-			patch -p1 < $(CURDIR)/fix_git_on_old_platforms.patch
-			;;
-		debian-9*)
-			patch -p1 < $(CURDIR)/fix_git_on_old_platforms.patch
-			;;
-	esac
+	if expr "$(OS)-$(OS_VERSION)" : "ubuntu-16.*" ; then patch -p1 < $(CURDIR)/fix_git_on_old_platforms.patch ; fi
+	if expr "$(OS)-$(OS_VERSION)" : "ubuntu-9.*"  ; then patch -p1 < $(CURDIR)/fix_git_on_old_platforms.patch ; fi
 
 	$(MAKE) install DESTDIR=$(CURDIR)/debian/tmp