zlib: really fix install for static only builds

Commit ab2f5567c1 (cleanup, fix install for static only build) forgot
to add the patch for static only builds, even though the commit message
mentioned it.

Thanks to Mike for noticing.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

CHANGES

@@ -4,7 +4,7 @@
 	compilation, and cache is stored in ~/.buildroot-ccache.
 
 	Updated/fixed packages: busybox, cloop, libconfig, m4,
-	openssh, openssl, qt, usbutils, xz
+	openssh, openssl, qt, usbutils, xz, zlib
 
 	New packages: dhrystone, lsuio, rsh-redone, whetstone
 

package/zlib/zlib-1.2.5-fix-static-install.patch

@@ -0,0 +1,24 @@
+[PATCH] fix make install for static builds
+
+Only try to install shared lib if we've built one.
+
+Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
+---
+ Makefile.in |    4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+Index: zlib-1.2.5/Makefile.in
+===================================================================
+--- zlib-1.2.5.orig/Makefile.in
++++ zlib-1.2.5/Makefile.in
+@@ -168,7 +168,9 @@ install-libs: $(LIBS)
+ 	-@if [ ! -d $(DESTDIR)$(man3dir)      ]; then mkdir -p $(DESTDIR)$(man3dir); fi
+ 	-@if [ ! -d $(DESTDIR)$(pkgconfigdir) ]; then mkdir -p $(DESTDIR)$(pkgconfigdir); fi
+ 	cp $(STATICLIB) $(DESTDIR)$(libdir)
+-	cp $(SHAREDLIBV) $(DESTDIR)$(sharedlibdir)
++	if test "$(SHAREDLIBV)" -a -f $(SHAREDLIBV); then \
++	  cp $(SHAREDLIBV) $(DESTDIR)$(sharedlibdir); \
++	fi
+ 	cd $(DESTDIR)$(libdir); chmod u=rw,go=r $(STATICLIB)
+ 	-@(cd $(DESTDIR)$(libdir); $(RANLIB) libz.a || true) >/dev/null 2>&1
+ 	-@cd $(DESTDIR)$(sharedlibdir); if test "$(SHAREDLIBV)" -a -f $(SHAREDLIBV); then \